l|f  i.  1.  m\n  TXtbrarg 


^nrtli  (Carolina  ^tatf  (Enllpg^ 


QK178 


K4 


^TURAL  RESOURCES 
UBKAKV 


I.e.    STATE    UNIVERSITY      D.H.    HILL    LIBRARY 


S00218871    R 


THIS  BOOK  IS  DUE  ON  THE  DATE 
INDICATED  BELOW  AND  IS  SUB- 
JECT TO  AN  OVERDUE  FINE  AS 
POSTED    AT    THE    CIRCULATION 


LIBRARY 

1992 


JUL  0  3  200b 


5M/7-87-871457 


U.  S.  DEPARTMENT  OF  AGRICULTURE. 

DIVISION   OF    BOTANY. 


CONTRIBUTIONS 


THE  U.  S.  NATIONAL  HERBARIUM. 

Vol.  V,  No.  5. 

ISSTJED    ^TJ&XJST   1,    1900. 


THE  PLANT  COVERING  OF  OCRACOKE  ISLAND;  A  STUDY 
IN  THE  ECOLOGY  OF  THE  NORTH  CARO- 
LINA STRAND  VEGETATION. 


THOMAS    H.    KEARNEY.    JR. 


OK  178 

K4 


WASHINGTON: 

GOVERNMENT    PRINTING    OFFICE. 

1900. 


m]t  ^,  ;i.  ^tll  %xhnxvn 


QKI78 
K4 


U.  S.  DEPARTMENT  OF  AGRICULTURE. 

DIVISION   OF   BOTANY. 


CONTRIBUTIONS 


THE  U.  S.  NATIONAL  HERBARIUM. 

Vol.  V,   No.  5. 
iswtjp:i:>  ^vuc^us'r  i,  looo. 


THE  PLANT  COVERING  OF  OCRACOKE  ISLAND;  A  STUDY 
IN  THE  ECOLOGY  OF  THE  NORTH  CARO- 
LINA STRAND  VEGETATION. 


THOMAS    PI.    KEAKNKY.    JR. 


WASHINGTON: 

GOVERNMENT    PRINTING    OFFICE. 
190  0. 


LETTER  OF  TRANSMITTAL 


U.  S.  Department  of  Agriculture, 

Division  of  Botany, 
Washington,  D.  C,  Fehruary  38,  1900. 
Sir:  I  have  the  honor  to  transmit  herewith,   for  i^ublication   as 
Volume  Y,  No.  5,  Contributions  from  the  United  States  National  Her- 
barium, a  manuscript  b}^  Mr.  T.  H.  Kearney,  jr.,  assistant  botanist, 
entitled  The  Plant  Covering  of  Ocracoke  Island. 

ResiDectfully, 

Frederick  V.  Coville, 

Botanist. 
Hon.  James  Wilson, 

Secretary  of  AgricuUiire. 

II 


CONTENTS. 


Page. 

Introduction 261 

Climate 262 

Temperature - 262 

Sunshine -  -   264 

Atmospheric  humidity.... 264 

Precipitation _ 265 

Wind - 266 

Physiography 266 

Geology  and  soils. 267 

The  plant  formations,  their  composition  and  physiognoijiy 260 

Sand-strand  vegetation 270 

Treeless,  open  formations 270 

Beach  formation 270 

Dune  formation 270 

Evergreen  tree  and  shrub  formations 271 

Tree  formation : 271 

Thicket  formation 272 

Salt-marsh  vegetation _ _ , 272 

Creek- marsh  formation 272 

Spartiua  stricia  association 272 

Jiincus  roemerianus  association 273 

Dune-marsh  formation 274 

Tidal  flat  formation 274 

Pasture  and  ruderal  plants  _.  275 

Cultivated  plants 275 

Ecological  forms  and  adaptations  to  environment  . . 275 

Adaptations  to  the  mechanical  action  of  the  wind  and  the  instability  of 

the  soil ^  276 

Adaptations  for  protecting  the  supply  of  water 277 

Anatomy . 280 

Species  of  the  sand  strand 285 

Panicum  amarutn 285 

Mnhlenbergia  filipes 285 

Spartina  patens 288 

Spartina  stricta. . 289 

Chloris  petraea 290 

Uniola  paniculata 292 

Yucca  aloif olia 298 

Yucca  gloriosa. '. 293 

Myrica  carolinensis 294 

Myrica  cerif era 294 

Quercus  virgini  ana  ... 294 

Zanthoxylnni  clava-herculis 295 

Croton  maritimus _ -   296 

III 


:V  CONTENTS. 

Anatomy — Continued.  Page. 
Species  of  the  sand  strand — Continued. 

Ilex  vomitoria ..- 296 

Oenothera  humifusa 297 

Teucrium  nashii 297 

Physalis  viscosa 298 

Salt-marsh  species  . - 301 

Triglochin  striata 301 

Spartina  stricta 301 

Juncus  roemerianus  .-. T^^ 

Sesuvium  maritimum i/ 

Tissa  marina r02 

Kosteletzkya  virginica 303 

Ammania  koehnei ?03 

Vincetoxicum  palustre. c  - j 

Lippia  nodiflora c04 

Monniera  monniera ^)5 

Solidago  sempervirens £05 

Aster  tenuif olius 306 

Aster  subulatus ._ 306 

Baccharis  halimifolia 307 

Iva  frutescens 508 

Borrichia  frutescens 309 

Geographical  affinities  of  the  flora - 312 

List  of  plants  collected  and  observed. 314 

Bibliography 319 


ILLUSTRATIONS. 


Fig.  33.  JIuhlenbergia  filipes — transverse  section  of  leaf 286 

34.  Muhlenhergia  filipes — ventral  epidermis  of  leaf 286 

35.  Mulilenhergia  filipes — dorsal  part  of  leaf  blade ^ 286 

36.  Muhlenhergia  filipes— xtortion  of  mestome  bundle 287 

37.  Chloris  p>etraea — leaf  blade. . .  . 290 

38.  Chloris  petraea — ventral  portion  of  leaf  blade 291 

39.  Chloris  petraea — large  mestome  bundle  from  leaf  blade. 291 

40.  Chloris  petraea— thx^e  small  mestome  bundles  from  the  blade 292 

41 .  Yucca  aloifolia — leaf  surface 293 

42.  Yucca  aloifolia — a  stoma - 293 

43.  Quercus  virgi^iiau a— stellate  hair  from  dorsal  leaf  surface 295 

44.  Croton  maritimus — hair  from  dorsal  leaf  surface 296 

45.  Physalis  v/scosjf— branched  hair  from  leaf  , 298 

46.  Tissa  ??iari?ia— glandular  hair  from  leaf  margin 302 

47.  Lippia  nodi/fora— stomata  and  hairs  .  „ 304 

48.  Iva  frutescens — hair  from  ventral  leaf  surface 308 

49.  Borrichia  frutescens — leaf  section 309 

50.  Borrichia  frutescens — leaf  hairs 309 


THE  PLANT  COVERIXG  OF  OCRACOKE  ISLAND:  A  STUDY 
IN  THE  ECOLOGY  OF  THE  NORTH  CAROLINA  STRAND 
VEGETATION. 


By  Thomas  H.  Kearney,  Jr. 


INTRODUCTION. 

In  October,  1898,  in  the  course  of  field  work  for  the  United  States 
Department  of  Agriculture,  the  writer  spent  five  days  upon  Ocracoke 
Ishmd,  North  Carolina.  Owing  to  its  limited  size,  it  was  possible, 
even  in  that  short  time,  to  explore  somewhat  thoroughly  a  considei*- 
able  part  of  the  island.  It  is  to  be  regretted  that  visits  were  not 
made  to  the  localit}^  earlier  in  the  season,  so  that  the  plienologieal 
develoj)ment  of  the  vegetation  could  be  studied.  However,  as  most 
of  the  characteristic  plants  of  our  southern  Atlantic  strand  are  rather 
late  in  maturing,  it  is  probable  that  a  better  season  for  a  single  visit 
could  not  have  been  chosen.  It  was  of  course  impossil)le  to  make 
any  valuable  observations  upon  fecundation  and  dissemination, 
important  as  these  subjects  are  to  the  study  of  the  geographical  dis- 
tribution of  plants.  AVliat  is  said  here  of  Ocracoke  will  doubtless 
apply,  in  a  general  Avay,  to  the  other  sandy  reefs  of  the  Xoi-tli  Caro- 
lina coast. 

The  object  of  this  paper  is  a  study  of  the  ecology  and  geography  of 
the  vegetation  of  the  island,  the  several  divisions  of  the  suliject  ))eiiig 
presented  in  the  following  order: 

(1)  Climate;  (2)  physiography;  (3)  geology  and  soils;  (4)  the  plant 
formations,  their  composition  and  physiognomy;  (5)  ecological  foinis — 
adaptations  to  environment;  (G)  anatomy;  (7)  phytogeograplnCal 
affinities  of  the  flora. 

The  nomenclature  used  is  mainly  that  followed  in  Hrittoii  and 
Brown's  Illustrated  Flora  of  the  Northern  United  States  and  Canada, 
but,  in  order  that  those  who  are  interested  in  ecological  work  and  are 
not  familiar  with  this  nomenclature  maj'find  no  difficulty  in  recognizing 
the  species  described,  the  names  used  in  the  later  works  of  Gray  and  of 
Chapman  are  quoted  in  parentheses.  A  full  list  of  all  plants  collected 
or  observed  upon  the  island  is  appended,  and  here,  again,  familiar  syno- 
nj^ms  are  cited  in  parentheses.  A  list  of  the  works  quoted,  Avith  their 
full  titles,  is  given  at  the  end  of  the  paper. 

In  the  i^reparation  of  the  anatomical  portion  of  the  pap<'r,   Mr. 

261 


-t!'J  THE    PLANT    COVERING    OF    OCRACOKE    ISLAND. 

1  heodor  Holm  has  rendered  valuable  assistance,  and  lie  has  kindly 
furnished  the  drawings  for  figures  Nos.  1  to  8,  17,  and  IS.  The  other 
figures  were  drawn  from  nature  hy  the  author. 

CLIMATE. 

The  following  data  have  been  obligingly  furnished  ])y  the  United 
States  Weather  Bureau.  The  observations  were  made  at  the  Hatteras 
Station,  only  a  few  miles  northeast  of  Oeracoke. 

TEMPERATURE. 

Readings  were  taken  in  the  shade.'  The  observations  at  Hatteras 
cover  a  period  of  about  twenty  years.  The  average  number  of  days 
per  annum  with  a  temperature  exceeding  6°  C.  (43°  F.)  is  365,  Avhile  at 
Norfolk,  Ya.,  the  number  is  only  295.  The  sum  total  of  temperatures 
above  6°  C.  during  the  year  averages  3,740.4:°  C.  (0,740°  F.),  which 
is  notably  higher  than  the  Norfolk  figure  of  3,359.4°  C.  (6,047.0°  F.). 
The  normal  mean  temperature  during  the  six  consecutive  hottest  weeks 
of  summer  is  25.0°  C.  (78.6°  F.),  as  compared  with  the  slightly  higher 
mean  of  26.3°  C.  (79.3°  F.)  at  Norfolk. 

The  normal  annual  temperature  is  16.3°  C.  (61.4  F.),  as  comimred 
with  14.8°  C.  (58.7°  F.)  at  Cape  Henry,  Virginia,  15.0°  C.  (59.0°  F.)  at 
Norfolk,  Va.,  and  17.2°  C.  (63.0°  F.)  at  Wilmington,  N.  C. 

The  normal  monthly  temperatures  are  as  follows: 


January  . 
February 

March 

April 

May 

June 


Degrees  C. 

Degrees  F. 

7.6 

1 
45.7  1 

8.1 

46.6 

10.0 

50.1  1 

u.o 

57.2  , 

19.1 

66.4  ; 

3:13 

74.0  ' 

.1 

Degrees  C. , Degrees  P. 


July 

August  . .. 
September 
October  .  . 
November 
December 


25. 5 

77.9 

2.5. 2 

77.4 

2:3.2 

7u.  7 

18.0 

64.5 

13.1 

55.6 

9.0 

48.2 

The  normal  daily  range  of  temperature  for  the  whole  year  amounts 
to  6.3°  C.  (11.3°  F.),as  compared  with  8.2°  C.  (14.7°  F.)  atCapellenry, 
8.8°  C.  (15.8°  F.)  at  Norfolk,  and  9.6°  C.  (17.3°  F.)  at  Wilmington. 

The  normal  dail}^  ranges  for  each  month  are  as  follows : 


January  . 
February 

March 

April 

May 

June 


Degrees  C. 

Degrees  F.jj 

7.0 

12.7 

7.1 

12.8 

7.2 

12.9 

6.9 

12.5 

6.4 

^ 

11.5 

5.7  1 

1 

10.3 

Degrees  C.  Degrees  F. 


July 

August 

September 
October  . . . 
November 
December . 


5.1 
5. 3 


10.0 
9.3 
9.6 
10.2 
11.3 
12.8 


'  Consequently  they  do  not  represent  the  temperature  to  which  most  of  the  vege- 
tation is  actually  exposed,  being  subject  to  insolation  during  the  hours  of  sun- 
shine.    They  are  chiefly  valuable  for  purposes  of  comparison  with  other  climates. 


TEMPERATURE    CONDITIONS. 


263 


The  absolute  maximum  temperature  observed  was  38. 8°  C.  (102°  F  ) 
as  compared  with  39.4°  C.  (103°  F.)  at  Cape  Henry,  38.8°  C.  (102°  F  ) 
at  Norfolk,  and  39.4°  C.  (103°  F.)  at  Wilmington. 

The  absolute  minimum  temperature  observed  w  as 13. 3°  C.  (8. 0°  F  ) 

ascomparedwith  — 15.0°  C.  (5.0°  F.)  at  Cape  Henry, —  1G.G°   C   (2  0^ 
F.)  at  Norfolk,  and  —  12.8°  C.  (9.0°  F.)  at  AVilmington. 

The  absolute  monthly  maxima  and  minima  are  as  follows: 


Month. 

Maxi 

mum. 

Minimum. 

Degrees  C. 

Degrees  F. 

Degrees  C. 

Degrees  F. 

Jamxary 

26.1 
22.8 
29.4 
30.0 
33.9 
38.8 
37.2 
36.1 

a5.o 

32.2 
26.1 

22.8 

79 
73 
85 
86 
93 
102 
99 
97 
95 
90 
79 
73 

-10.0 
-11.7 

-  3.3 

-  0.6 
6.1 

12. 8 
16.1 
16.6 
10.0 
5.5 

-13.3 

February. 

U 

March... 

11 

April.. 

26 

May... 

31 

June 

43 

July 

55 

August 

61 

September  _ 

62 

October 

50 

November 

43 

December 

28 

8 

The  average  date  of  the  latest  killing  frost  in  spring  is  February 
25,  as  compared  with  March  19  at  Cape  Henry,  March  2G  at  Norfolk, 
and  March  15  at  Wilmington.  The  latest  recorded  was  April  5,  as 
compared  with  April  19  at  Cape  Henry,  April  26  at  Norfolk,  and  April 
20  at  Wilmington. 

The  average  date  of  earliest  killing  frost  in  autumn  is  December  13, 
as  compared  with  November  14  at  Norfolk  and  Cape  Henry  and 
November  12  at  Wilmington.  The  earliest  killing  frost  recorded  was 
on  November  12,  as  compared  with  November  14  at  Cape  Henry,  Octo- 
ber 15  at  Norfolk,  and  October  13  at  Wilmington. 

From  the  above  data  the  temperature  may  be  characterized  as  fol- 
lows: Warm,  but  not  excessive,  with  a  considerable  sum  total  of 
effective  temperatures  during  the  growing  season,  and  usually  mild 
temperatures  during  the  very  brief  dormant  period.  The  normal 
temperature  is  at  least  (j.5°  C.  above  freezing  point  during  every 
month  of  the  year.  The  normal  amount  of  daily  variation  of  tem- 
perature is,  according  to  the  season,  from  5°  to  7°  C,  a  relatively 
very  small  range.  The  period  between  the  average  dates  of  the 
earliest  killing  frost  in  autumn  and  of  the  latest  in  spring,  which  may 
be  taken  as  very  roughly  coinciding  Avith  the  dormant  period  of  most 
of  the  vegetation,  covers  only  seventy-four  days. 


264  THE    PLANT   COVERING    OF    OCRACOKE    ISLAND. 

SUNSHINE. 

The  observations  cover  a  period  of  nearly  thirty  years.  Normal 
annual  sunshine,^  stated  in  percentages  of  possible  sunshine,  54,  as 
compared  with  52  at  Cape  Henry,  51  at  Norfolk,  and  52  at  Wilming- 
ton.    The  monthly  percentages  are  as  follows: 


Month. 


January 
February 
March  .. 
April 


Per 
cent. 


Month. 


May — 
June . . , 
July... 
August 


Per 

cent. 


Month. 


Per 

cent. 


September 
October... 
November 
December 


Normal  annual  sunshine,  stated  in  Irours,  2,392.2,  as  compared  with 
2,314.G  at  Cape  Henry,  2,270.1  at  Norfolk,  and  2,312.7  at  Wilmington. 
The  normal  monthly  number  of  hours  of  sunshine  are: 


Month. 

Hours. 

Month. 

Hours.                  Month. 

Hours. 

144.7 
143.7 
193.4 
216.0 

Mav                 

256.2      September 

208.3 

February 

March  

AT»ril 

238.9      October... 

203.0 

July 

243.1      November 

167.4 

August - 

216.9   j  December 

160.6 

1 


These  records  yield  the  result  that  the  normal  annual  percentage 
of  sunshine  is  low  compared  with  that  in  much  of  the  territory  of  the 
United  States,  especially  west  of  the  Mississippi  River;  but  it  is  not 
much  less  than  that  prevailing  in  other  parts  of  the  Southeastern 
States,  while  it  exceeds  the  percentages  given  for  the  northern  portion 
of  the  Atlantic  slope. 

ATMOSPHERIC  HUMIDITY. 

This  is  stated  in  percentages  of  possible  saturation,  which  of  course 
varies  at  different  seasons  with  the  temperature,  etc.  Annual  (for  a 
period  of  seven  years),  81.4  as  compared  with  74  at  Cape  Henry,  and  73 
(during  nine  years)  at  Norfolk  and  Wilmington.     Monthly,  as  follows : 


Month. 


Per 
cent. 


January  . 
February 
March  — 
April 


Month. 


Per 
cent. 


Month. 


May  — 
June  ... 
July.... 

August 


September. 

October 

November. 
December  . 


Per 
cent. 


The  annual  percentage  thus  shown  is  greater  than  that  recorded 
for  any  other  station  in  the  United  States,  excepting  those  in  the 

'  These  figures  only  approximate  the  real  values.     They  are  derived  from  statis- 
tics of  cloudiness. 


RAINFALL. 


265 


Puget  Sound  region,  and  even  there  the  excess  over  the  Hatteras 
figure  is  not  great.  Moreover,  this  humiditj^  is  distributed  throughout 
the  months  of  the  year  with  remarkable  uniformity,  the  variation 
between  any  two  months  amounting  to  not  more  than  o  per  cent. 

PRECIPITATION. 

This  is  stated  in  centimeters  and  inclies.  Annual,  159.4  centimeters 
{66.41  inches),  as  compared  with  125.6  centimeters  (52.34  inches)  at 
Cape  Henrj^,  125.0  centimeters  (52.1  inches)  at  Norfolk,  and  130.4 
centimeters  (54.34  inches)  at  Wilmington.     Monthlj^,  as  follows: 


Month. 


January. 
February 
March  . . . 
April 


Cen- 
time- 
ters. 


14.3 
10.7 
14.6 
11.3 


Inch 
es. 


5.91 
4.47 
6.10 
4.73 


Month. 


May  ... 
June... 
July... 
August 


Cen- 
time- 
ters. 


11.0 
10.9 
15.4 
15.3 


Inch- 
es. 


4.60 
4.57 
6.43 
6.a5 


Month. 


September 
October  . . . 
November 
December . 


Cen- 
time- 
ters. 


Inch- 


15. 4 
14.8 
13.4 
13.1 


ti.44 
6.17 
5.18 
5.47 


The  average  annual  number  of  rainy  days  is  123.8,  as  compared 
with  125  at  Cape  Henry,  131.3  at  Norfolk,  and  128.8  at  Wilmington. 
The  average  monthl}^  number  of  raiu}^  days  is  as  follows : 


Month. 

Days. 

Month. 

Days. 

1 
Month.                   Days. 

January , 

15.9 
10.3 
11.9 

8.4 

May 

June        

10.0 
9.6 

10.3 
10.3 

September 13.7 

February 

October 7.5 

July 

November 6.7 

April 

August 

December 9.5 

At  Hatteras  the  precipitation  consists  almost  entirely  of  rain.  Rain- 
bearing  storms  usually  approach  from  a  westerl}'  direction.  AVinter  and 
spring  rains  are  usuallj^  of  light  intensity  and  long  duration,  while 
those  of  the  summer  and  fall  are  more  often  brief  and  torrential  in 
character. 

The  results  viewed  comparatively  are  as  follows:  Tlie  normal 
annual  rainfall  is  remarkably  heavy,  exceeding  that  at  the  nearest 
station,  Wilmington,  by  30  centimeters.  Only  on  the  coast  of  Wash- 
ington and  Oregon  does  the  total  rainfall  within  tlie  limits  of  tlie 
United  States  notably  exceed  that  of  Hatteras.  The  normal  varia- 
tion between  the  month  of  least  and  that  of  greatest  rainfall  does 
not  exceed  5  centimeters,  so  that  in  ordinary  seasons  periods  of 
drought  do  not  occur.  The  heaviest  rainfall  occurs  in  tlie  months  from 
July  to  October.  The  average  number  of  rainy  days  is  large,  about 
one-third  of  the  days  of  the  year,  and  is  distributed  with  relatively 
great  uniformity,  varying  from  6.7  days  in  the  montli  of  least  to  15.9 
in  the  month  of  greatest  number  of  rainy  days. 

Of  dewfall  no  statistics  could  be  obtained. 


266 


THE    PLANT    COVERING    OF    OCRACOKE    ISLAND. 


WIND. 

The  average  annual  maximum  velocity  of  the  wind  is  21.4  kilome- 
ters (13.3  miles)  per  hour,  as  compared  with  23.2  kilometers  at  Cape 
Henry,  15.1  at  Norfolk,  and  15.4  at  Wilmington.  The  average  monthly 
maximum  velocities,  stated  in  kilometers  and  miles,  are  as  follows: 


Month. 


January. 
February 
March . . . 
April 


Kilo- 
me- 
ters. 

Miles 

25.0 

15.5 

24.5 

15.2 

25.2 

15.6 

24.2 

15.0 

Month. 


May  ... 
June . . . 
July... 
August 


Kilo- 
me- 
ters. 

Miles 

20.3 

12.6 

21.3 

13.2 

18.5 

11.5 

19.7 

12.2 

Month. 


September 
October . . . 
November 
December. 


Kilo- 
me- 
ters. 


17.2 

18.4 
19.8 
24.0 


Miles 


10.7 
11.4 
12.3 
14.9 


In  regard  to  direction,  the  winds  of  midwinter  are  usually  from  the 
north,  while  those  of  midsummer  are  usually  from  a  little  west  of 
south. 

As  thus  shown,  the  average  velocity  of  the  wind  is  considerable,  and 
the  amount  of  its  variation  from  month  to  month  is  remarkably"  slight. 
The  highest  average  of  course  prevails  in  winter  and  early  spring.  In 
midwinter,  when  the  winds  are  normally  strongest  and  therefore  most 
affect  the  perennial,  especially  the  woody  vegetation,  their  prevailing 
direction  is  almost  due  south  (from  the  north),  hence,  in  the  case  of 
Ocracoke,  from  tlie  mainland. 

In  regard  to  temperature,  rainfall,  and  atmospheric  humidity  the 
climate  of  Ocracoke  and  Hatteras  is  suitable  for  a  vigorous  forest 
growth.  But  the  exposure  to  strong  winds,  and  the  peculiar  soil  con- 
ditions, neutralize  these  favorable  factors  and  give  it  a  typical  strand 
vegetation,  which  much  resembles  that  of  deserts.  In  the  neighbor- 
hood of  Norfolk  and  of  Wilmington,  where  conditions  of  temxjerature 
and  of  humidity  are  really  somewhat  less  suitable  than  at  Hatteras  to 
the  most  luxuriant  develo]3ment  of  j^lants,  the  virgin  growth  is  almost 
eveiywhere  dense  forest,  because  there  the  inimical  conditions  are 
absent. 

PHYSIOGRAPHY. 

Ocracoke  Island  is  part  of  that  long  chain  of  narrow  sand  reefs 
which  fringes  the  southern  Atlantic  Coast  of  the  United  States,  and 
which  forms  the  eastern  bariier  to  a  series  of  almost  land-locked  bays 
and  sounds.  Ocracoke  lies  in  longitude  76°  west  and  latitude  35°  10' 
north,  and  is  therefore  somewhat  south  of  the  center  of  the  North 
Carolina  coast.  It  is  separated  from  Hatteras  Reef  by  the  0.8  kilo- 
meter (one-half  mile)  wide  strait  known  as  Hatteras  Inlet,  and  from 
Portsmouth,  the  next  island  below,  by  Ocracoke  Inlet,  3  kilometers 
(nearly  2  miles)  wide.  Ocracoke  itself  is  about  26  kilometers  (16 
miles)  in  length,  and  extends  from  that  great  bulge  of  the  coast  line 


GEOLOGY    OF    THE    ISLAND.  267 

known  as  Cape  Ilatteras,  in  a  southwesterly  direction.  Tlio  islancrs 
greatest  width  near  its  lower  end  falls  short  of  3  kilometers;  the  aver- 
age width  is  only  1  kilometer,  while  in  places  it  is  even  narrower. 
Outside  rolls  the  Atlantic,  while  between  island  and  mainland  stretch 
the  waters  of  Pamlico  Sound,  here  from  30  to  45  kilometers  (18  to  27 
miles)  wide.  Pamlico  differs  from  the  shallower  Albemarle  Sound  1o 
the  north  in  the  important  respect  that  its  water  is  always  salt,  while 
Albemarle  is  normally  fresh. 

Near  the  so tith western  extremity  of  the  island  a  broad  expanse  of 
tidal  flat  separates  the  higher  land  of  the  village  of  Ocracoke  from 
the  Atlantic  beach.  One  and  one-half  kilometers  or  so  toward  the 
northeast  this  lagoon  disappears,  and  dry  land  extends  from  the  flat 
sandy  beach  and  the  salt  marshes  which  border  the  Sound  to  the 
dunes  which  front  the  ocean.  Into  these  marshes  penetrate  tiny 
ci'eeks,  whose  ramifications  cut  the  lower  part  of  the  island  in  all 
directions.  Almost  the  whole  area  is  divided  between  sand  strand 
and  tidal  mai'sh.  Much  of  it  is  only  1  meter  or  less  above  normal 
high  tide  and  subject  to  overflow  when  strong  easterly  gales  a  re  blow- 
ing, or  when  stiff  breezes  from  the  opposite  quarter  mass  the  waters 
of  Pamlico  Sound  against  the  western  shore  of  the  island.  The  high- 
est land  on  Ocracoke  is  rex^resented  by  sand  dunes  often  3,  sometimes 
8  meters  high.  These  are  usually  regular  in  form  and  fairly  well 
fixed  by  the  vegetation.  Those  that  abut  upon  the  outer  beacli  or 
rise  amid  the  mud  flats  are  particularly  regular  and  dome-shaped. 

GEOLOGY  AND  SOILS. 

Of  the  geology  of  Ocracoke  and  its  neighbor  Ilatteras,  we  have 
comparatively  little  knowledge.  Shaler^  has  jidvanced  the  theory 
that  these  reefs  were  built  up  from  the  detritus  which  resulted  from 
the  glacial  excavation  of  Delaware  and  Chesapeake  bays.  Kerr- 
describes  Ilatteras  as  a  "sort  of  delta."  "The  action,"  he  says,  "of 
the  tides  and  ocean  ctirrents,  the  Gulf  stream  and  Arctic  current 
meeting  at  this  i^oint,  accumulates  upon  Ilatteras  tlie  river  silt  wliieh 
reaches  the  sea  by  way  of  the  Chesapeake  as  well  as  that  of  tin'  rivers 
which  discharge  their  burdens  through  the  inlets  about  this  point  ami 
southward.  *  *  *  Ilatteras  is  not  a  modern  phenomenon.  It  is 
at  least  as  old  as  the  Cretaceous;  tlie  Quaternary  as  well  as  tlie  Ter- 
tiary of  this  coast  region  of  North  Carolina  are  laid  down  ui)on  an 
eroded  surface  of  Cretaceous  rock."  From  measnrements  elsewhere 
made,  the  probable  depth  beneath  the  surface  of  the  Cretaceons  for- 
mation on  Ilatteras  and  (Ocracoke  would  be  somewliere  between  I'on 
and  300  meters.     lam  not  aware  that  borings  of  any  <'onsiderabhMleptJi 


1  Proc.  Bost.  Soc.  Nat.  Hist.,  vol.  14,  pp.  110  to  121.     1872. 
•^Bul.  Wash.  Phil,  boc,  vol.  (5,  pp.  '-38  to  :JU.     1884. 


268  THE    PLANT    COVERING    OF    OCRACOKE    ISLAND. 

have  been  made  upon  these  islands.^  Kerr  further  states  that  * '  the  reef 
is  increasing  in  continuity  and  breadth."  But  this  is  not  the  gen- 
eral opinion,  for  it  is  said  that  there  is  to-daj'  water  of  considerable 
depth  where  houses  stood  upon  Ocracoke  within  the  memory  of  living 
men,  and  it  is  stated^  that  "a  fine  fig  orchard  and  many  peach  trees, 
with  a  fine  potato  patch  and  garden,"  occupied  earlier  what  is  now 
Hatteras  Inlet.  That  the  present  tendency  of  this  whole  coast  line  is 
one  of  subsidence  can  hardly  be  disputed. 

Beneath  the  superficial  Recent  deposits  of  dune  sands  and  salt- 
marsh  silt  which  cover  the  greater  part  of  the  island  lie  the  sands 
and  clays  of  the  Columbia  formation,  which  extend  to  a  considerable 
but  unascertained  depth.  This  and  the  Recent  accumulations  are 
the  onh^  geological  formations  of  this  part  of  the  coastal  plain  which 
need  be  considered  in  relation  to  the  existing  plant  covering. 

Excepting  the  areas  occupied  by  creeks  and  salt  marsh,  the  soil  of 
Ocracoke  is  a  fine  white  marine  sand,  almost  everywhere  devoid  of 
any  considerable  admixture  of  humus.  Only  in  the  live-oak  groves 
is  there  enough  A^egetable  matter  present  to  give  the  sand  a  gray 
color.  There  is  doubtless  some  quantity  of  calcium  carbonate  in  the 
soil,  owing  to  the  presence  of  small  particles  of  shells  washed  up  by 
the  waves  and  scattered  b}^  the  wind.-^ 

As  much  of  the  island  is  subject  to  occasional  inundation  and  to 
the  deposition  of  spray  by  the  winds,  the  soil  content  of  sodium  chlo- 
rid  must  be  considerably  greater  at  times  than  in  ordinary  inland  soils.^ 
There  is  no  lack  of  moisture  in  this  sandy  substratum.  Even  in  the 
driest  looking  beach  sand,  water  usually  stands  at  a  depth  of  only  15 
to  30  centimeters  (6  to  12  inches)  from  the  surface.  The  superficial 
layer  of  the  sand  acquires  a  great  amount  of  heat  on  sunny  days  and 
becomes  thoroughly  desiccated,  in  which  condition  it  is  subject  to 
being  blown  about  by  the  wind,  its  degree  of  coherenc}^  depending 
upon  the  character  of  the  vegetation.  At  night,  however,  sand  gives 
up  its  heat  rapidly  and  absorbs  much  dew,  if  conditions  are  favorable.'^ 

The  soil  of  the  salt  marsh,  which  appears  to  be  usually  a  thin  sheet 

'  The  succession  of  strata  in  the  North  Carolina  coastal  plain,  where  exposed 
in  the  valleys  of  the  Neuse  and  Cape  Fear  rivers,  is  given  as  follows,  beginning 
with  the  oldest: 

(1)  Potomac  gravel,  sands,  and  clays. 

(2)  Cretaceous  sands  and  clays. 

(3)  Tertiary  (Eocene  and  Miocene)  marls  and  clays. 

(4)  Lafayette  (yellowish  and  brownish  sands  and  loams). 

(5)  Columbia  sands,  gravels,  and  clays. 

2W.  L.  Welch,  Bui.  Essex  Inst.,  vol.  17,  pp.  87  to  42.     1886. 

■^According  to  Contejean  (Geogr.  Bot.),the  proportion  of  calcium  carbonate 
thus  supplied  to  the  strand  soils  is  insignificant  except  near  the  wave  limit,  the 
particles  being  soon  dissolved  by  the  carbon  dioxide  contained  in  rain  water  and 
then  washed  down  through  the  readily  permeable  soil. 

^Sea  water  contains  from  2.7  to  3.2  per  cent  of  NaCl. 

^Warming,  Lehrbuch,  p.  66. 


ECOLOGICAL    CROUPS.  269 

of  fine,  brown  silt  overlying  a  stiff,  bluish  ehiy,  contains  orj^^anic  mat- 
ter in  considerable  quantity  and  is  therefore  capable  of  supporting  a 
denser  plant  growth  than  is  found  upon  the  sands.  It  is  of  course 
saturated  with  salt  or  brackish  water. 

There  is  no  outcrop  of  any  kind  of  rock  on  tlic  island. 

THE   PLANT    FORMATIONS,    THEIR   COMPOSITION    AND    PHYSIOG- 
NOMY. 

The  various  assemblages  of  species  and  individuals  which  make  up 
the  plant  covering  of  Ocracoke  Island  may  be  classified  as  follows:* 

L  Sand-strand  vegetation. 
1.  Treeless  (open). 

(a)  Beach  formation:  Croton-Physalis  association. 

(b)  Dune  formation:  *  Uniola-Yucca  association. 
3.  Evergreen  trees  and  shrubs. 

(a)  Tree  formation:  Quercus  virginiana  association. 
(6)  Thicket  formation:  Ilex  vomitoria  association. 

II.  Salt-marsh  vegetation. 

1.  Creek-marsh  (closed)  formation. 

(a)  Spartina  stricta  association. 

(b)  Juncus  roemerianus  association. 

3.  Dune-marsh  formation;  Lippia-Monniera  association. 
3.  Tidal  flat  (open)  formation:  Sesuvium-Tissa  association. 

III.  Pastures  and  ruderal  plants. 

IV.  Cultivated  plants. 

It  is  not  to  be  supposed  that  the  severial  groups  are  always  or  even 
commonly  sharply  defined.  On  the  contrary  the  transition  from  one 
to  another  is  almost  always  gradual,  so  that  iDortions  of  the  plant 
covering  are  difficult  to  classify.  Nevertheless,  the  formations  and 
associations  are  distinct  features  of  the  landscape,  easily  recognizable 
by  any  observer. 

' It  has  seemed  best  to  use  the  word  ''formation *'  in  the  same  sense  as  employed 
by  the  German  and  most  other  plant  geo-raphers— i.  e.,  to  designate  ihe 
larger  assemblages.  For  more  restricted  groups,  whether  composed  of  one  or 
many  species,  the  term  ''association''  is  to  be  preferred.  The  nearly  ejuivalent 
German  word  "Verein"'  is  used  as  a  translation  of  the  Danish  "Sanifuud"  in 
one  of  the  most  important  works  on  the  subject  (Warming,  Lehrbuch)  for  the 
larger  assemblages  or  formations;  but,  in  the  want  of  a  better  English  word  it  has 
been  thought  expedient  to  employ  '' association  *' for  the  more  restricted  assem- 
blages, which  are  peculiar  to  each  biogeographical  area.  While  the  ft^rmations  are 
purely  ecological  elements  which  recur  in  the  strand  vegetation  of  other  regions, 
being  for  the  most  part  closely  dependent  upon  topographical  features,  the  asso- 
ciations are  often  quite  local;  and  owe  much  of  their  character  to  the  particular 
groups  of  species  which  compose  them. 

'  It  is  not  possible  to  distinguish  here  several  dune  formations,  such  as  occur, 
for  example,  on  the  coast  of  Virginia. 


_^70  THE    PLANT    COVERING    OF    OCUACOKE    ISLAND. 

SAND-STRAND  VEGETATION. 
TREELESS,   OPEN   FORMATIONS. 
BEACH   FORMATION. 

This  forination  occurs  along  Pamlico  Sound,  occupj'ing  the  flat  or 
gently  sloping  sandy  beach,  especially  toward  the  lower  end  of  the 
island.  The  species  are  almost  all  herbaceous  and  usually  form  an 
open  vegetation,  leaving  much  of  the  soil  uncovered.  The  most 
abundant  is  Croton  maritimus,  which  sometimes  grows  rather  closely, 
excluding  other  species.  By  reason  of  its  silvery-gray  color,  due  to  a 
close,  stellate,  scale-like  pubescence,  it  is  one  of  the  most  conspicuous 
plants  of  the  island.  It  is  usually  stout  and  often  much-branched. 
Another  noteworthy  plant  is  Physalis  viscosa,  a  perennial  herb,  Avith 
slender  roots,  sometimes  1.5  meters  long,  creeping  near  the  surface  of 
the  sand,  and  sending  up  at  intervals  short  leaf}'  shoots.  Its  color 
varies  from  green  to  gray  with  the  density  of  its  covering  of  branched 
hairs.  An  interesting  feature  of  this  formation  is  the  occurrence  in 
places  of  diminutive  thickets  onl}"  1  to  3  decimeters  high,  composed 
chiefly  of  Ilex  vomHoria  {I.  cassine  of.  authors),  Zanthoxylon  cJara- 
herculiSy  Juniperus  virginiana,  with  leaves  only  of  the  spreading  form, 
and  Opuntia  pes-corvi,  with  its  long  spines.  Among  other  species 
belonging  to  the  beach  formation,  there  are  of  annual  herbs  En- 
pliorhia  polygonifoUa,  Triplasis  purpurea,  a  canescent  form  of  Sola- 
num  nigrum,,  a  large-fruited  Xanthium,  and  Salsola  kali,  the  last 
being  the  most  abundant;  of  perennial  herbs  Teucrium  imsliii,  with 
slender  stolons  and  white-tomentous  lower  leaf  surface,  Chloris 
petraea,  with  decumbent  culms,  rooting  at  the  nodes,  Panicum  neu- 
ranthum,  and  occasional!}'  CaprioJa  dactylon  {Cynodon  dadylon 
Pers.);  of  woody  plants  Buhus  trivial  is  and  Smilax  boua-iwx  oecnr 
here  and  there,  with  prickly  stems  trailing  over  the  sand. 

DUNE   FORMATION. 

Open  dunes  are  occupied  chieflj^  b}'  the  handsome  sea  oats,  Uniola 
paniculata,  the  most  characteristic  strand  plant  of  the  Southeastern 
States.  The  low,  rounded  dunes  Avhich  rise  from  a  bare  pebbly 
shingle  on  the  ocean  side  of  the  island,  and  here  and  there  in  the 
tiiidst  of  the  tidal  flats,  support  no  other  vegetation.  The  leafy 
shoots  of  this  grass  are  iDroduced  in  great  abundance,  but  flowering 
branches  are  much  less  numerous.^  Mulilenhergia  filipes  is  abundant 
on  and  among  the  dunes,  its  delicate  purplish  panicles,  swaj-ing  with 
the  lightest  breath  of  air,  ]3resenting  a  most  beautiful  appearance. 
It  is  almost  the  only  cespitose  plant  of  the  island,  and  grows  in 
tufts  that  are  sometimes  3  decimeters  in  diameter.     Rather  small 

'  In  this  respect  the  Uniola  resembles  Ammophila  arenaria,  which  takes  its 
place  farther  north. 


TREE    FORMATION.  271 

plants  of  Yucca  gloriosa,  with  fleshy  rootstocks  often  exposed  by  the 
shifting  of  the  sands,  are  frequent  on  the  lesser  dunes.  The  sinjjjle 
specimen  of  Yucca  aloifolia  observed  was  over  2  meters  high,  with 
stem  branched  several  times  above  the  ground.  Botli  species  have 
exceedingly  hard  and  sharp  spinous  leaf  tips.  On  some  of  the  liiglier 
dunes  depauperate  plants  of  the  shrubby  il/?/rica  caroVniensiii^  mostly 
onl}^  3  to  6  decimeters  high,  associate  with  the  Uniola.  Of  secondary 
importance  in  this  association  are  two  perennial  grasses,  Paniruyyi 
amarurn  minus  and  Spartina  patens  (juncea);  as  well  as  a  probably 
biennial  thistle,  Carduus  spinosissimus  (Cnicus  horridulus) ;  and 
several  other  herbs,  among  them  the  white-sericeous  Oeuothera  humi- 
fusa  and  Croton  maritimus. 

EVERGREEN   TREE    AND   SHRUB   FORMATIONS. 

TREE   FORMATION. 

Scattered  over  the  island,  but  preferring  the  higher  dunes  which 
occupy  its  inner  side,  are  small  groves  of  live  oak,  Quercus  virgin  tana 
(Q.  virens),  either  in  pure  association  or  mixed  with  some  other  trees. 
The  oaks  are  usually  6  to  9  meters  high  and  3  (rarely  7^)  decimeters 
in  diameter.  Those  on  the  northern  edges  of  the  groves  have  trunks 
strongly  inclined  toward  the  south,  and,  as  a  consequence  of  the  deiUi- 
dation  of  the  branches  on  the  windward  side,  the  whole  crown  of 
foliage  lies  to  leeward  of  the  axis.  One  could  not  desire  a  better 
indication  of  the  prevailing  direction  of  strong  winds  in  the  region.^ 
The  branches,  gnarled  and  twisted,  are  clad  with  numerous  lichens, 
chiefly  Usnea  barbata,  and  with  occasional  small  wisps  of  Spanish 
moss  {Tillandsia  usneoides),  which  evidently  maintains  but  a  precari- 
ous foothold  on  the  trees  of  this  wind-exposed  island. 

Altogether  the  aspect  of  the  groves  is  rather  weird  and  somber. 
Often  associated  with  the  oaks  are  small  trees  of  Mijrica  cerifera,  Zan- 
ihoxyluin  clava-Jierculis  and  Ilex  vomitoria,  all  of  about  the  same  maxi- 
mum size  (G  meters  high  and  2  decimeters  in  diameter),  and  occasionally 
Ju7iiperus  virgimana,  which  rarelj"  attains  a  height  of  *J  meters  and  a 
diameter  of  3  decimeters.  Lianas  are  sparingly  represented  by  S)n  ila.v 
hona-nox,  Vitis  aestivalis,  and  Rhus  radicans,  all  three  species  some- 
times attaining  considerable  size  and  climbing  to  the  tree  tops.  The  last 
is,  however,  usuall}^  of  the  creeping  form,  with  the  main  stem  under- 
ground. The  herbaceous  members  of  this  association  are,  in  the 
smaller  groves,  chiefly  plants  characteristic  of  the  open  strand,  Cldoris 

'All  the  specimens  of  live  oak  seen  were  apparently  of  considerable  a2re.  Seed- 
lings were  few  or  none,  and  no  acorns  were  observed.  It  is  probable  that  instead 
of  increasing,  the  oak  is  here  holding  its  ground  with  difficulty.  So  highly  are  the 
trees  valued  as  wind-breaks  by  the  inhabitants  that  none  are  felled,  all  fuel  being 
brought  from  the  mainland.  The  rounded  shrubby  form  of  this  plant,  common 
elsewhere  on  the  coast,  was  not  observed  on  Ocracoke. 


272  THE    PLANT    COVERING    OF    OCRACOKE    ISLAND. 

petraea,  Physalis  viscosa,  Diodia  teres,  etc.,  and  the  difference  in  soil 
and  light  is  not  sufficiently  great  to  cause  any  apparent  modification 
in  the  plants.  In  larger  groves,  where  the  light  is  more  diffused  and 
some  humus  collects,  Oplismeniis  setarius  ^  covers  the  ground  with  its 
creeping  stems,  associated  with  such  normally  shade-loving  species 
8is  Sanicula  sp.y  Aspleniuni  platyneuron  {A.  ebenoides),  Uniola  laxa 
(U.  gracilis),  Panicinn  laxiflorurn  and  two  mosses,  growing  on  the 
ground,  Brymn  argenteum  and  Rhynchostegium  serrulatuni. 

THICKET   FORMATION. 

Thickets  of  I/ex  vomitoria,  by  far  the  most  abundant  woody  plant 
of  Ocracoke  Island,  often  cover  the  low  dunes,  especially  near  the 
inner  side  of  the  island.  The  plants  are  here  usually  10  to  20  deci- 
meters high,  with  short,  rigid,  thorn-like  branches,  light-gray  bark, 
thick  evergreen  leaves  and  bright  scarlet  berries.  The  branches  are 
often  shaggy  with  lichens,  notably  Ramcdina  montagnei.  Occasion- 
ally the  Ilex  gives  place  to  small,  dense  thickets  of  Myrica  carolinen- 
sis,  sometimes  4^  meters  high.  This  formation  corresponds  in  a 
measure  to  the  "Maquis"  or  "Garrigues"  of  the  western  Mediter- 
ranean region.^  The  herbaceous  species  that  have  established  them- 
selves among  these  shrubs  are  chiefly  such  as  are  most  abundant  on 
the  beach  and  open  dunes.  Two  thin-leaved,  shade-loving  herbs  are 
occasional,  Fariefaria  dehilis  with  weak,  much-branched  stems,  and 
Melotliria  pendida,  with  twining  stems. 

SALT-MARSH   VEGETATION. 
CREEK-MARSH   FORMATION. 

Salt  marshes  fringe  all  the  small  creeks  and  ditches  that  intersect 
the  lower  part  of  the  island,  and  sometimes  cover  broader  tracts  imme- 
diately bordering  the  sound  Avith  a  growth  that  is  almost  everywhere 
dense  and  reed-like.  'I'wo  rather  sharply  defined  belts  are  distinguish- 
able along  the  larger  creeks,  an  outer,  covered  chiefly  with  Spartlna 
stricta,  and  an  inner,  where  Juncus,  roemerianus  predominates.  The 
latter  alone  occupies  the  small  creeks  and  ditches  which  are  farthest 
from  the  beach. 

SPARTINA   STRICTA    ASSOCIATION. 

The  Spartina  prefers  the  edge  of  open  water,  where  it  is  in  large 
part  submerged  at  high  tide.  It  has  a  light,  yellow-green  color  dur- 
ing the  growing  season,  but  is  brown  and  discolored  much  of  the  year. 
The  stems  are  usually  about  6  decimeters  high.  Scdicornia  herbacea, 
often  bright  red  and  conspicuous,  grows  rather  abundantly  with  the 

'  In  southern  Mississippi,  also,  I  found  this  species  growing  only  in  the  shade  of 
Qiiercus  virginiana. 
2  Compare  Grisebach,  Veg,  der  Erde,  vol.  1,  pp.  294,  328,  etc. 


SALT-MARSH    VEGETATION.  273 

grass.^     Distichlis  spicata  {D.   maritima)  usually  accompanies   this 
association,  but  is  not  of  primary  importance. 

JUNCUS  ROEMERIANUS   ASSOCIATION. 

The  Juncus  roemerianns  association  occupies  mucli  more  ccround 
than  that  of  Spartina,  and  comprises  a  much  larger  number  of  species. 
It  is  best  developed  on  land  that  is  merely  wet  a  great  part  of  the  time, 
and  covered  with,  at  most,  only  a  few  centimeters  of  water  at  high 
tide.  The  Juncus  is  of  a  dark-green  color,  and  usually  reaches  a 
height  of  about  1  meter,  making  a  dense  growth  of  stiff,  sharp- 
pointed  stems  and  leaves.  Among  the  secondary  members  of  tliis 
association  certain  grass-like  plants  occur  locally  in  some  quantity. 
Notable  are  Chaetochloa  iniberhis  perennis,  with  weak,  slender  culms 
from  short,  knotted  rootstocks,  preferring  the  borders  of  the  niarsli, 
and  Tijplia  laiifolia^  usually  standing  in  water  of  some  depth.  Spar- 
tina patens  {8.  juncea)  is  occasional,  the  salt-marsh  form  being  smaller 
and  more  slender  than  that  which  grows  upon  the  sand  strand.  Pas- 
palum  distichum  and  Distichlis  spicata  are  also  met  with  in  more  open 
places  among  the  Juncus. 

Compositae,  with  mostly  rather  succulent  leaves,  are  conspicuous, 
especially  near  the  margin  of  this  association.  Aster  tenuifolius,  a 
slender  rush-like  perennial  species  whose  few  branches  terminate  in 
solitary,  rather  large  heads  with  showy  white  rays,  is  less  abundant 
than  the  related  Aster  subukitus,  a  much-branched,  often  rather  stout 
annual  Avith  numerous  inconspicuous'heads.  SoTidago  sempervirens 
and  Baccliaris  halimifolia  s^re  most  at  home  on  the  edge  of  the  Juncus 
growth.  Both  are  showy  plants,  the  latter  with  bright  white  pappus, 
the  former  with  a  golden-yellow  panicle.  Borrichia  fridescens,  one  of 
the  most  characteristic  i^lants  of  the  strand,  ]3refers  comparatively 
open  spots  where  the  ground  is  merely  wet.  It  has  a  stout  stem, 
usualh^  3  to  6  decimeters  high,  thick  whitish  leaves,  and  yellow  sun- 
flower-like heads.  Iva  fridescens  is  the  most  abundant  composite  of 
the  marshes,  almost  always  associating  with  the  Juncus.  Two  climl)- 
ing  plants,  Galactia  volid)ilis  {G.  pilosa)  ii\\(\  Vincetoxicum  palustre, 
a  glabrous,  narrow-leaved  asclepiad,  occur  near  the  edges  of  the  marsli, 
twining  around  the  stems  of  the  rushes  and  other  plants.  Atriplej- 
hastata  is  occasional  in  similar  situations.  Even  Ilex  voniitoria  some- 
times strays  into  the  marsh,  growing  among  the  Juncus  as  a  hnv 
straggling  shrub. 

Somewhat  different  is  the  assemblage  of  species  about  the  small 
pools  that  frequently  interrupt  the  growth  of  Juncus  roemerianus. 

'Likewise  in  southwestern  France,  Spartina  stricfa  and  Salicornia  herhacea 
form  the  outermost  association  in  soil  that  is  submerged  at  high  tide.  (Conte- 
jean,  Geogr.  Eot.,  p.  56.)  According  to  Warming  (Lehrlmch.  p.  307)  Salworuia 
herhacea  grows  unmixed  with  other  species  as  the  outermost  embryophylic  vegeta- 
tion on  the  eastern  shores  of  the  North  Sea.  S2)artina  atrieta  does  not  range  so 
far  north  in  Europe. 
2965 2 


274  THE    PLANT    COVERING    OF    OCRACOKE    ISLAND. 

Their  borders  are  the  favorite  habitat  of  a  characteristic  malvaceous 
plant,  Kosteletzhya  virginica,  which  has  rather  thin,  pubescent  leaves 
and  large  rose-colored  flowers.  AVith  it  grow  a  species  of  Rnmex, 
Ipomoea  sagittata,  Solidago  semper virens,  Cladium  effusum  (a  stout 
sedge  with  sharply  saw-edged  leaves),  Panicum  ivalteri,  and,  very 
conspicuous  where  it  occurs,  Andropogon  glomeratus  {A.  macrourus). 
In  the  shallow  water  of  these  pools  grows  Monniera  monniera  {Her- 
pestis  monniera  H.  B.  K.)  in  its  aquatic,  partially  submerged  form 
with  elongated  stems,  as  well  as  Ammannia  hoehnei,  Phichea  ccnn- 
pliorata,  and  a  species  of  Eleocharis. 

DUNE-MARSH   FORMATION. 

A  low,  rather  scanty  vegetation  covers  limited  areas  of  wet  sand 
which  fringe  the  reed  marsh,  separating  it  from  the  dry  strand,  and 
also  occurs  here  and  there  in  depressions  among  the  dunes.  The 
most  characteristic  species  are  the  terrestrial  form  of  Monniera  vion- 
nier a  ^yith  short  internodes,  and  Lippia  nodiflora,  both  having  repent 
stems  rooting  at  frequent  intervals  and  leaves  usually  appressed  to 
the  ground.  In  the  case  of  Lippia,  however,  the  leaves  are  sometimes 
nearly  vertical  in  strong  sunlight,  giving  the  plant  a  peculiar  appear- 
ance. Each  of  these  species  sometimes  occupies  small  tracts  to  the 
exclusion  of  other  vegetation.  They  usually  grow  together,  however, 
and  in  association  with  Hydrocotyle  umhellata,  Centella  asiatica,  and 
Diodia  virginiana,  all  small  plants  with  creeping  or  prostrate  stems. 
Among  the  dunes  Lippia  and  Herpestis  sometimes  play  a  less  impor- 
tant part,  and  an  assemblage  of  species,  some  of  which  are  not  nor- 
mally halophilous,  covers  the  ground.  Of  these  Juncus  dichoiomus, 
J.  scirpoides,  Scirpus  americanus  {S.  piingens),  Trigloch in  striata,  and 
Mikania  scandens  are  more  at  home  in  saline  soils,  while  Ludwigia 
7nicrocarpa,  L.  alata,  Cynoctouuni  mitreola  {Mitreola  petiolata),  and 
Dicliromena  colorata  (D.  leucocepliala)  are  character  plants  of  the 
fresh- water  marshes  of  the  region.  Such  commingling  is  perhaps  to 
be  explained  by  the  fact  that  these  hollows  among  the  dunes  derive 
their  moisture  largely  from  the  rainfall,  while,  on  the  other  hand, 
siDray-laden  winds  contribute  a  certain  amount  of  salt  to  the  soil. 

TIDAL   FLAT   FORMATION. 

This  is  an  open  formation,  occupying  the  margins  of  the  shallow 
lagoon  at  the  lower  end  of  the  island,  which  is  under  water  at  flood 
tide.  The  soil  is  a  mixture  of  silt  and  sand.  A  sparse  growth  of 
Sesurium  maritimuni  (S.  pentandrum),  Tissa  marina  {Lepigonum 
salinum),  and  Scirpus  americanus  forms  a  characteristic  association. 
Faspalum  disticlimn,  with  prostrate  culms,  sometimes  2  meters  long, 
rooting  at  the  nodes,  as  well  as  scattered  erect  tufts  of  Fimbristylis 
spadicea,  were  the  only  other  species  observed  in  this  formation. 


ECOLOGICAL    FORMS.  275 

PASTURE  AND  RUDERAL  PLANTS. 

A  oonsidenible  area  towards  tlie  lower  end  of  Ocraeoke,  (^specially 
in  and  near  the  village,  is  covered  with  a  fine  turf  composed  almost 
entire!}"  of  Capriola  dactylon,  closely  grazed  by  horses,  cattle,  and 
sheep.  Here  and  there  over  these  pastures  are  scattered  groups  of 
various  weeds,  notably  Cassia  occidentalism  Sporoholus  indicus,  and 
Solarium  carolinense,  as  well  as  a  species  of  Xanihium,  Bidens  hipin- 
nata,  Chenopodium  antlielmiidicum,  Ambrosia  artimisiaefolia^  Ver- 
hascum  fliapsus^  etc.,  all  of  which  have  undoubtedly  l)een  importe<l 
into  the  island  b}^  the  agency  of  man.  Occasionally,  strays  from  the 
indigenous  formations  are  met  with  here.  Fleshy  fungi  are  sparingly 
represented. 

CULTIVATED  PLANTS. 

As  far  as  was  ascertained,  the  only  plants  now  cultivated  upon  the 
island  are  fig  trees  {Ficus  carica),  which  are  planted  about  dwellings 
and  freely  mature  their  fruit  in  this  mild  climate.  Small  paper  mul- 
berry trees  {Broussonetia  papyrifera)  are  established  in  door  yards. 
According  to  a  statement  above  quoted,  peach  trees  and  potatoes  wore 
formerly  grown.  Attempts  to  cultivate  garden  vegetables  are  usually 
terminated  by  inroads  of  the  sea  during  a  gale,  which  leave  the  soil 
strongly  impregnated  with  salt. 

ECOLOGICAL  FORMS  AND  ADAPTATIONS  TO  ENVIRONMENT. 

In  considering  the  i:)hysical  environment  of  plants  upon  Ocracoke 
Island,  and  the  various  modifications  of  the  vegetative  organs  whereby 
they  are  adapted  to  their  medium,  it  is  evident  that  many  of  the  latter 
fall  readily  into  two  categories :  (1)  Adaptations  protecting  against  the 
mechanical  action  of  the  wind^  and  the  unstable  nature  of  the  soil; 
and  (2)  modifications  that  assist  the  plant  to  increase  or  conserve  its 
supply  of  water.  Sand-strand  and  salt-marsh  species  alike  require 
both  sorts  of  modifications,  although  the  latter  formation  is  less 
exposed  to  Avind  and  the  shifting  of  its  substratum.  However,  n(^t 
oidy  the  vegetation  upon  loose  sand,  but  that  which  covers  the  muddy 
bottom  of  the  salt  marshes,  must  accommodate  itself  to  a  more  or  less 
incoherent  and  mobile  soil.  To  the  first  category  are  to  be  referred 
most  of  the  noteworth}^  life  forms  of  the  island,  i.  e.,  those  in  which 
the  epharmonic  peculiarities  of  structure  (such  as  are  due  to  tlu' 
direct  action  of  the  physical  environment)  extend  to  the  entire  organ- 
ism. To  the  second  belong  chiefly  modifications  of  a  part  icular  organ, 
the  leaf. 

^The  exposed  position  of  the  island,  and  its  consequent  relative  poverty  in  large 
woody  growth,  renders  herbaceous  vegetation  here  more  than  usually  subject  to 
the  action  of  the  wind. 


NATURAL  RESOURCES 


276  THE    PLANT    COVERING    OF    OCRACOKE    ISLAND. 

ADAPTATIONS  TO  THE  MECHANICAL  ACTION  OF  THE  WIND  AND 
THE  INSTABILITY  OF  THE  SOIL. 

A  notable  characteristic  of  the  vegetation  is  the  prevalence  of  low 
forms.  Tall  stems  (more  than  1  meter  high)  among  herbaceous  species 
which  are  not  grass-like,  are  almost  wanting.  Often  the  stems  creep 
above  or  below  the  surface  of  the  ground  and  root  at  intervals. 

Lippia  nodiflora,  Monniera  monniera,  Capriola  dactylon,  and  Pr/.s- 
paliim  disfichum  have  stems  creeping  upon  the  surface.  These  may 
be  regarded  as  humble  representatives  of  the  Pes-caprae  form,  which 
is  so  characteristic  of  tropical  strands.^  Species  possessing  creeping 
subterranean  stems,  from  which  arise  subaerial  leaf}^  and  flowering 
branches,  are  Panicum  amarum  minus  and  Uniola  p>aniculata,  as  well 
as  many  of  the  salt-marsh  plants,  notably  Juncus  roemerianus,  Typlw 
Jafifolia,  and  Spartina  stricta,  whose  strong,  creeping  rhizomes  form  a 
dense  sod  in  the  loose  mud.  In  Uniola paniculat a  the  rootstock  is  stout 
and  descends  obliquely  or  almost  vertically  deep  into  the  sand. 
Pliy sails  viscosa  has  a  long,  slender,  branching  root,  Avhich  creeps 
horizontally  often  a  distance  of  a  meter  or  more  near  the  surface,  and 
originates  at  intervals  erect,  leaf 3^  and  flowering  branches.  Teucriurn 
nasliii  i)ossesses  thickish  stolons,  which  arise  in  the  axils  of  the  scale- 
like, lowest  leaves. 

Other  species  growing  on  the  sands  have  prostrate  stem  branches, 
which  do  not  root  after  leaving  the  main  axis.  These  may  be  long  and 
trailing,  as  in  the  woody  Rubus  trivialis,  or  short  and  radiating  in  all 
directions  from  the  primary  axis  as  in  certain  annuals,  Diodia  teres,  D. 
virginiana,  Jlollugo  verticillata,  and  Eupliorhia  polygon  if olia,  as  well 
as  the  biennial  Oenothera  humifusa.  This  radiant  form,^  as  we  may 
term  it,  is  not  so  abundant  and  characteristic  here  as  at  other  points 
along  the  Atlantic  coast  of  the  United  States. 

The  cespitose  form  is  apparentlj^  not  well  adapted  to  conditions 
upon  Ocracoke,  for  it  is  well  developed  only  in  Mulilenhergia  filipes. 

The  shrubs  and  trees  of  the  island  show  the  effect  of  much  exposure 
to  high  wind  in  their  short  gnarled  branches  and  in  the  often  one- 
sided position  of  their  crown  of  foliage,  the  last  peculiarity  being 
especially  noticeable  in  the  live  oak.  Here,  however,  w^e  have  to  do 
rather  with  the  direct  mechanical  effect  of  the  wind  than  with  a  pro- 
tective modification. 

As  further  adaptations  against  the  coast  winds,  whose  destructive- 
ness  to  tender  vegetation  must  be  greatly  increased  by  the  quantity 
of  sand  they  carry,  should  be  cited  the  great  development  of  mechan- 
ical tissue  in  the  leaves  of  many  species — e.  g.,  Uniola  panicuUda, 
Juncus  Toemerianus,  Quercus  virginiana — and  the  strong  thickening 
of  the  outer  cell  walls  of,  the  epidermis,  to  which  is  due  the  hard  pol- 

'  Schimper,  Indo-Mal.  Strand-flora,  p.  78. 

■'  Schimper  (Strand-flora,  p.  81 )  describes  this  form  as  occurring  in  the  East  Iiidian 
strand  vegetation.  ;  t:^'^>.  ^     .»^. 


COLLECTION  AND  STORAGE  OF  WATER.         277 

ished  surface  exhibited  hy  the  larger  grass-like  plants  and  by  the 
evergreen  leaves  of  Quercus  and  Ilex.  This  last  peculiarity  is,  how- 
ever, doubtless  primarily  induced  by  the  necessity  f<jr  protection 
against  loss  of  water. 

ADAPTATIONS  FOR  PROTECTING  THE  SUPPLY  OF  WATER. 

Strand  iDlants  upon  Ocracoke  Island,  unlike  deser^^^  plants,  are  not  to 
any  noteworthy  extent  equipped  with  special  apparatu.4  for  collect  ing  or 
for  storing  water,  if  we  except  the  development  of  water-storage  tissue 
in  several  of  the  salt-marsh  species.  The  obvious  reason  is  the  aljsence 
of  a  period  of  drought,  there  being  at  all  times  a  relatively  high  per- 
centage of  water  in  the  air  and  the  soil.  On  the  other  hand,  both 
maritime  and  desert  vegetations  are  characterized  by  certain  pecul- 
iarities of  structure,  especially  of  the  leaves,  which  are  usually- 
denominated  xerophytic,  albeit  these  are  less  strikingly  developed  in 
strand  plants  than  in  those  which  inhabit  deserts.  Such  common 
points  of  resemblance  are,  as  isAvell  known,  due  to  a  common  necessity 
for  i)rotection  against  excessive  loss  of  water  by  transpiration  from 
the  leaves,  and  this  despite  the  abundant  supply  of  water  in  the 
environment  of  strand  plants. 

In  the  case  of  salt-marsh  vegetation  it  is  chiefly  the  presence  of  a  com- 
paratively high  percentage  of  sodium  chlorid  in  the  soil  water  which 
necessitates  a  xerophytic  structui-e.  Jtist  how  this  salt  reacts  upon 
the  life  processes  of  plants  and  what  the  precise  mode  is  by  which 
i:)lants  iDrotect  themselves  against  its  injurious  effects  are  much  mooted 
questions.^ 

^  Con te jean  (Qeogr.bot.  ,pp.71,94)  holds  that  salt  is  harmful  to  most  plants;  that 
it  is  not  indispensable  even  to  strand  plants,  and  that  the  latter  are  confined  to  an 
otherwise  unfavorable  habitat  merel}'  by  their  inability  to  compete  in  the  struggle 
for  existence  with  the  salt-shunning  species  of  nonsaline  soils.  That  this  view  is 
only  partially  correct  is  suggested  by  the  known  tendency  of  halophilous  (salt- 
loving)  species  to  take  up  greater  quantities  of  sodium  chlorid,  even  when  grown 
in  nonsaline  soils,  than  do  jDlants  which  are  not  halophilous. 

Schimper  (Strand-flora,  pp.  2o,  26)  attributes  to  the  accumulation  of  sodium  chlo- 
rid in  the  green  tissue  an  injurious  effect  upon  assimilation,  particularly  upon  the 
production  of  starch  and  sugar.  More  recently  (Pflanzengeogr.,  p.  IOC)  he  modi- 
fies this  view,  but  still  emphasizes  the  importance  of  a  chemical  action  of  the  salt 
upon  metabolism,  the  synthesis  of  proteids  being  the  process  cliiefiy  affectcl. 

In  order  to  reduce  this  deleterious  action  to  a  minimum,  the  accumulation  of 
sodium  chlorid  in  the  tissues  must  be  as  far  as  possible  retarded.  This  is  accom- 
plished, according  to  Schimper's  theory,  by  diminishing  root  osmosis  and  hence 
the  volume  of  the  ascending  colunm  of  water  holding  the  chlorid  in  solution, 
this  end  being  secured  by  means  of  certain  modifications  of  leaf  structure  that 
reduce  the  volume  of  transpired  water.  Besides  this  chemical  effect,  Schimper 
also  admits  a  direct  physical  infiuence  which  the  presence  of  common  salt  in  the 
soil  exerts  upon  the  process  of  osmosis.  As  Sachs  (Landw.  Versuchsst.  vol.  1,  p. 
223)  demonstrated  by  experiment,  the  roots  of  ordinary  plants  take  ud  with  diffi- 
culty water  which  holds  in  solution  sodium  chlorid  as  well  as  other  salts  nota- 
bly calcium  sulphate),  a  difficulty  that  of  course  increases  with  the  concentration 


2(8  THE    PLANT    COVERING    OF    OCRACOKE    ISLAND. 

Factors  in  the  iDlij^sical  environment  of  sand-strand  vegetation 
which  tend  to  accelerate  transpiration  from  the  surface  of  the  jDlant, 
and  hence  contribute  to  the  necessity  for  xerophytic  structure,  are : 

1.  Exposure  without  shelter  to  the  almost  continual  and  often  vio- 
lent movement  of  air  currents,  which  keep  the  plant's  atmospheric 
envelope  constantly  changing  and  prevent  it  from  approaching  a  con- 
dition of  saturation. 

2.  Intense  light,  both  direct  and  reflected  from  the  surface  of  the 
sand.  Light,  which  becomes  converted  into  heat  in  the  chlorophyll 
tissue,  increases  transpiration  ^  in  proportion  to  its  intensity.  Besides 
this  effect  of  light,  its  direct  and  harmful  action,  when  too  intense, 
upon  the  chlorophyll  is  to  be  guarded  against,  and  this  is  probably 
effected  bj^  some  of  the  modifications  which  also  serve  to  reduce 
transpiration.  But  in  the  present  state  of  our  knowledge  it  is  imj)os- 
sible  to  discriminate  between  the  respective  modifications  Avhich 
protect  the  plant  against  these  two  effects  of  light. 

3.  Great  heat  during  a  great  part  t)f  the  year.  Much  more  intense 
than  the  atmospheric  heat  is  that  which  is  absorbed  by  and  reflected 
from  the  superficial  layer  of  sand.^ 

It  is  probable,  however,  that  the  i)resence  of  a  high  percentage  of 
sodium  chlorid  in  the  substratum  is  at  least  as  effective  as  any  of 
these  causes  in  bringing  about  xerophytic  structure.     This  is  evident 

of  the  solution.  Whether  this  is  equally  true  of  halophilous  species  is  not 
established. 

L.  Diels  ( Jahrb.  Wiss.  Bot.  vol.  23,  p.  316)  doubts  that  osmosis  in  plants  of  saline 
soils  is  sufficiently  reduced  to  account  for  the  absence  of  accumulations  of  salt  to 
an  injurious  extent  in  the  tissues.  He  found  that  salt-marsh  plants  when  trans- 
ferred to  distilled  water  showed  a  steady  loss  of  salt  from  day  to  day,  although  the 
impossibility  of  an  excretion  of  the  sodium  chlorid  as  such  could  be  demonstrated. 
This  author  gives  a  number  of  analyses  of  halophilous  species  which  would  indi- 
cate that  in  plants  of  that  character  the  cells  are  enabled  to  decompose  the 
accumulated  sodium  chlorid,  the  sodium  probably  uniting  with  malic  acid,  while 
the  chlorin  possibly  combines  with  water  and  passes  off  through  the  roots  as 
hydrochloric  acid.  It  is  known  that  xerophytic  modifications  which  protect  the 
plant  against  excessive  transpiration  at  the  same  time  cause  an  increased  evolu- 
tion of  tree  acids  (notably  malic  acid)  in  the  green  tissue,  by  preventing  the 
ready  access  of  oxygen  and  otherwise  hindering  the  exchange  of  gases  between 
the  plant  and  the  atmosphere.  These  researches  of  Diels,  if  confirmed  for  halo- 
philous plants  generally,  will  prove  an  insuperable  objection  to  Schimper"s  theory 
that  such  plants  can  prevent  an  indefinite  accumulation  of  sodium  chlorid  in 
their  tissues  only  by  reducing  root  action  and  hence  transpiration.  If  we  accept 
Diels's  conclusions,  v/e  should  have  to  refer  the  xerophytic  structure  of  halophilous 
plants  largely  to  its  efficacy  in  preventing  a  f  re-3  exchange  of  gases  between  plant 
and  atmosphere,  thus  rendering  imperfect  the  combustion  of  carbohydrates  in  the 
plant  tissues  and  occasioning  the  production  of  considerable  quantities  of  organic 
acids,  which  serve  the  plant  by  decomposing  the  absorbed  sodium  chlorid. 

'Wiesner,  Untersuch.,  p.  506. 

2  Volkens  (Fl.  .^gypt.,  p.  14)  found  a  difference  of  from  22^  to  24°  C.  between  the 
temperatures  of  the  surface  soil  and  of  the  atmosphere  in  the  shade  near  Cairo,  in 
Egypt,  the  maximum  heat  of  the  sand  being  55°  C. 


MEANS    OF    REDUCING    TRANSPIRATION.  279 

when  we  examiue  the  siill-inarsh  vegetat  iuii.  Must  of  the  species  of 
tliat  formation,  even  those  wliieh  are  wliolly  or  partially  submerj^ed 
at  high  tide,  possess  siieh  structure.  No  plants  of  th<'  North  Carolina 
strand  are  more  conspicuously  xerophytie  in  structure  than  Salirornid 
lierhacea  and  Spartina  stride.  That  such  structure  is  closely  related 
to  the  ability  to  take  up  NaCl  in  considerable  (iuantities  is  i)nn  cd  \)y 
the  fact  that  certain  species  which  do  not  naturally  inliahit  saline 
soils,  but  wdiich  possess  strongly  developed  modifications  airaiust 
excessive  transpiration,  can  absorb  that  salt  in  ([uautilics  ihai  are 
fatal  to  plants  not  so  constituted.  ^ 

For  this  reason  species  belonging  respectively  to  the  saml  si  rand 
and  to  the  salt  marsh  of  Ocracoke  Island  are  not  distinguished  in  lh<3 
following  enumeration  of  the  means  by  which  transpiration  is  i«'<l  nc-d. 

1.  Reduction  of  the  transpiring  surface. 

(a)  Leaves  small:  Ilex  vomitoria  ( smallest-leaved  of  our  species  of  llexj,  Gakic- 
tia  rolubiUs  (unusually  narrow-leaved  form.) ,Vincetoxicinii palast re,  Tis.sd  marina 
(leaves  liemicylindrical),  Monniera  monniera,  Lippia  xodijiora  (leaves  notably 
smaller  than  in  nonsaline  soils),  Se.KKvium  maritimum,  etc.  Most  of  the  species 
enumerated  have  small  or  narrow  leaves  as  compared  with  the  nearest  related 
inland  forms. 

(b)  Leaves  scale-like,  their  functions  transferred  to  the  stem,  which  is  succu- 
lent; stem  succulents:  Opuntia  pes-eorvi,  Saliconiia  licrbacea. 

(c)  Leaves  conduplicate  or  involute,  especially  in  dry,  sunny  weather,  so  that 
only  the  dorsal  surface  is  exposed:  All  the  grasses,  and  Cladiioa  effusnm,  Fim- 
bristi/Us  s2Jadice((,  and  other  sedges.  In  the  f^rasses  this  characteristic  is  corre- 
lated with  the  position  of  the  stomata,  which  lie  at  the  bottom  of  furrows,  espe- 
cially on  the  unexposed  ventral  surface,  and  are  further  protected  from  air  currents 
by  a  network  of  hairs  which  line  the  walls.  In  Quercua  viryiniana  the  leaf  mar- 
gins frequently  become  more  or  less  revolute. 

Ul)  Leaves  iDerfectly  terete  and  in  structure  little  ditferentiated  from  the  stem: 
Juncus  roemeria n  us, 

2.  Position  of  the  transpiring  surface,  leaves  vertical  or  nearly  so:  Many  of  the 
grasses  and  sedges,  Tijplia,  Juncus  roemeria  mis,  Friijloehin  striata,  yonui^  leaves 
of  Yucca  spp.,  Lippia  nodiflora  (sometimes),  Vincetoxicum  palustre  (leaves 
reflexed) ,  the  Compositae. 

'S.  Development  of  protective  modifications  in  the  epidermis. 

(a)  Thickened  cuticle:  Many  species,  notably  the  larger  grass-like  plants  and 
woody  species  with  evergreen  leaves.  A  shining  upper  leaf  surface,  as  in  Ih\c 
vomitoria,  may  he  of  use  by  reflecting  some  of  the  incident  light  rays,  as  has  been 
suggested  by  Wiesner. 

(b)  Waxy  covering:  Panicum  amarum,  Uniola  panicidata,  Euphorbia  poly- 
gonifolia,  etc.  This  character  is  but  slightly  developed  in  the  vegetation  of  Ocra- 
coke Island. 

((')  Hairy  covering:  Oenothera  hnmifusa  and  Teucriuin  )iashii  (hairs  long, 
simple);  Quercus  riryiiiiana  (stellate  hairs  on  the  dorsal  surface  only):  Kiisteletz- 
kija  virginica  and  Croton  maritimus  (hairs  stehate,  scale-like):  Phijsidis  risco.sa 
(hairs  forked);  BorricJtiafrutescens  (youngleaves  very  densely  covered  with  short 
hairs,  giving  the  surface  a  glistening  appearance).  Interesting  hairs  also  occur 
on  other  species,  but  not  in  sufficient  numbers  to  serve  as  a  protective  covering 
(except  in  the  leaf  furrows  of  certain  Gramineae). 


Schimper,  Pt^anzenge(igr.,  \).  0".). 


280  THE    PLANT    COVERING    OF    OCRACOKE    ISLAND. 

4.  Succulency. 

(a)  Stem  succulents:  Opuntia  jpes-corvi ,  Salicornialierhacea. 

(b)  Leaf  succulents:  Fncca  spp.,  Tissa  marina,  Sesuvium  mar itimum,  Euphor- 
bia polygonifolia,  Vincefoxicum  palustre,  Aster  subidahis,  A.  flexuosus,  Solidago 
sempervirens — mostly  salt-marsh  species.  Not  only  does  the  increase  in  thickness 
of  the  leaf  serve  directly  as  a  protection  against  excessive  loss  of  water,  but  the 
thickening  tissue  consists,  in  most  cases,  of  colorless,  water-storage  parenchyma, 
which  is  peculiarly  tenacious  of  its  water  supply. 

5.  Structure  of  the  chlorenchyma. 

Nearly  all  the  species,  of  both  sand  strand  and  salt  marsh,  are  characterized  by 
the  development  of  palisade,  a  compact  chlorophyll  tissue  with  cells  more  or  less 
elongated  at  a  right  ang-'.e  to  the  surface  and  occupying  the  exposed  face  or  faces — 
i.  e.,  the  ventral  face  in  bifacial  leaves,  both  faces  in  such  as  are  isolateral.  Such 
tissue  is  believed  to  have,  among  other  functions,  that  of  protecting  against  ex- 
cessive loss  of  water  the  remainder  of  the  leaf  (the  interior,  or  the  lower  face,  as 
the  case  may  be) ,  which  is  usually  occupied  by  less  compact  tissue. 

6.  Aromatic,  volatile  oil. 

An  oil  of  this  character  is  secreted  by  the  species  of  Myrica.  It  has  been  sug- 
gested, although  the  idea  needs  substantiation,  that  the  possession  of  such  oils 
affords  protection  againsr  excessive  loss  of  water  by  the  formation  about  the  plant 
of  an  envelope,  which  is  less  pervious  to  heat  rays  than  is  ordinary  air.  At  any 
rate  this  is  a  frequent  attribute  of  plants  inhabiting  very  dry  regions.' 

Not  to  be  interpreted  as  affording  protection  against  excessive 
transpiration,  yet  perhaps  largely  dne  to  the  inflnence  of  conditions 
that  necessitate  such  protection,  is  the  develoinnent  of  short,  rigid, 
almost  thornlike  branches  {IJex  vomitoria)  and  of  prickles  and  spines 
(Smilax,  Biihus  trivialis,  Opnntia,  Zanthoxylum,  leaf  apices  of  the 
species  of  Yucca).  Probably  the  depauperate  form  assumed  by  some 
of  the  woody  species  when  growing  on  the  beach  is  similarly  explicable.^ 

Strong  thickening  of  the  under-ground  parts  for  storage  of  reserve 
food  materials  does  not  occur  in  many  si)ecies.  The  only  notable 
cases  detected  were  Smilax  hona-nox  (rootstocks  with  tuberous  thick- 
enings), Yucca  spi^.  (rootstocks  large,  fleshy),  and  KosteJetzkya  vir- 
gin ica  (root  stout,  Avoody,  vertical). 

ANATOMY. 

In  almost  all  cases  the  histological  structure  of  the  leaf  alone  is 
here  considered,  that  being  the  organ  which  shows  most  plainly 
adaptations  to  certain  factors  of  the  environment,  notably  those 
wiiich  affect  transpiration.  The  general  peculiarities  of  leaf  anatomy 
in  the  vegetation  of  the  sand  strand  and  of  the  salt  marsh,  respec- 
tiveh^,  are  first  enumerated,  and  the  resemblances  and  differences  of 
plants  of  the  two  formation  classes  are  liointed  out.  Several  of  the 
more  important  species  of  each  category',  in  all  thirty-two,  are  then 

^Haberlandt,  Pflanzenanat.,  p.  325.     Volkens,  Fl.  ^gypt.,  p.  46. 

'^A  like  depressed  habit  is  characteristic  of  shrubs  growing  above  the  limit  of 
trees  in  high  latitudes  and  altitudes.  It  is  usually  attributed  to  exposure  to  strong, 
dry  winds,  which  is  probably  the  chief  factor  in  its  development  on  the  beach  of 
Ocracoke  Island. 


PROVISIONS    FOR    CONSERVING    WATER.  281 

taken  up  and  described  in  sj-stematic  order.  Tables  sliowini,^  wlial 
are  believed  to  be  the  characters  that  are  most  iinportanl  from  an 
ecological  point  of  view  have  been  prepared  for  tlie  two  <^m-()iii)s  of 
species.  For  a  nnmber  of  species  the  material  studied  was  not 
obtained  npon  Ocracoke  Island,  but  from  simihir  situations  on  the 
coast  of  Virginia,  and  in  all  such  cases  tlie  source  of  tlie  spefim«Mis 
used  is  mentioned.  In  some  cases  comparisons  are  made  with  rehited 
species,  usually  from  other  formations,  in  order  to  make  clear  the 
differential  characters  of  the  strand  species. 

In  a  great  majority  of  the  sand  strand  plants  the  leaf  is  bifacial, 
the  two  species  of  Yucca  being  the  only  exceptions  noted.  In  some 
species  this  specialization  is  imperfect,  as  in  Oenothera  humifusd.  \n 
other  cases  the  differentiation  of  the  two  sides  of  the  leaf  is  com- 
plete, as  in  Quercus  virginiana.  In  most  cases  the  leaf  is  thick  as 
com]3ared  with  the  same  organ  in  related  nonmaritime  species.  Good 
examples  are  the  evergreen,  leather}^  leaves  of  Quercus  virfjiniana 
and  Ilex  romltoria,  as  well  as  the  leaves  of  the  two  grasses,  Uniola 
paniculaia  and  Panicuin  amarum.  A  stronglj^  thickened  cuticle  is 
.  an  almost  invariable  character,  and  this  is  conspicuously  wrinkled  in 
a  few  species.  The  lateral  walls  of  the  epidermis  cells  are  undulate 
in  four  species,  viz,  the  comparatively  thin-leaved  Cliloris  petraea, 
Teucrium  iiasliii,  and  Phy sails  viscosa,  and  tlie  thick-leaved  Ilex 
vomit  or  la. 

Half  of  the  species  have  stomata  on  both  leaf  surfaces,  but  in  every 
such  case  they  are  especially  protected — in  the  grasses  by  being  sit- 
uated in  furrows;  in  the  species  of  Yucca  by  being  deeply  sunken, 
and  in  Physalis,  Oenothera,  and  Croton  b}'  a  covering  of  hairs.  In 
the  wood}^  species  they  are  always  on  the  dorsal  or  lower  surface  only, 
and  in  Quercus  virginiana  they  are  further  protected  by  a  hairy  cov- 
ering (as  also  in  the  herbaceous  Teucrium  nashll). 

Hairs  form  a  dense,  i)rotective  covering  on  both  leaf  sui-faecs  of 
Oenothera,  Croton,  and  Physalis,  which  species  have  stomata  on  both 
surfaces:  only  on  the  dorsal  surface  in  Quercus  and  Teucrium,  agree- 
ing with  the  i^osition  of  the  stomata  on  that  surface  only.  In  Quercus 
and  Croton  the  hairs  are  pluricellular  and  stellate;  in  Physalis  iIh.n 
are  irregularly  branched;  in  Oenothera  and  Teucrium  they  are  elon- 
gated, unbranched,  and  unicellular.  Teucrium  also  possesses  slioi-t, 
glandular,  cai)itate  hairs. 

The  chloroi3h3dl  tissue  is  homogeneous  in  the  monocotyledons  of 
the  sand  strand,  while  in  the  dicotyledons  it  is  more  or  less  difTereii- 
tiated  into  palisade  on  the  ventral  side  of  the  leaf  and  pneumatic 
tissue  on  the  dorsal  side.  The  palisade  is  mostly  quite  compact,  but 
never  of  more  than  3  and  usually  of  only  1  or  2  layers. 

Colorless  parenchyma,  which  probably  performs  the  function  of 
water-storage  tissue,  occurs  in  consideral)le  quantity  only  in  the 
grasses  and  the  species  of  Yucca. 


282  THE    PLANT    COVERING    OF    OCRACOKE    ISLAND. 

Stereome  occurs  subepidermally  (especially  in  the  leaf  margins)  in 
the  Gramineae  only.  In  most  of  the  species  of  the  sand  strand,  how- 
ever, it  is  found  as  a  support  to  the  mestome  bundles.  These  are 
furthermore  reinforced  by  hj'podermal  collenchyma  or  collenchymatic 
tissue  in  most  of  the  dicotyledonous  species,  this  tissue  probably  serv- 
ing as  a  protection  against  loss  of  water  by  evaporation  from  the 
vessels. 

The  sand-strand  grasses  deserve  further  mention  with  reference  to 
their  leaf  structure.  It  belongs  to  a  type  of  which  Chloris  petraea 
exhibits  one  extreme  and  Muhlenberg m  filipes  the  other — the  type 
exhibited  by  most  grasses  of  deserts  and  steppes.  The  salt  marsh 
Spartina  stricta  exhibits  a  wholly  similar  arrangement  of  tissues. 

The  margins  are  more  or  less  conduplicate  or  involute  when  the 
supply  of  water  is  small,  becoming  flat  when  moisture  is  plentiful, 
except  in  the  leaf  of  Muhlenhergia  filipes,  which  is  conduplicate,  with- 
out power  to  unfold,  and  appears  as  if  terete.  The  result  of  this 
adaptation  is  that  in  dry,  sunny  weather  only  the  dorsal  leaf  surface 
is  directly  exposed  to  the  air  and  light.  In  Panicum  amarinn  and 
Chloris  ]petraea  the  movement  is  effected  by  true  bulliform  cells,  while 
in  the  other  grasses  (except,  of  course,  Muhlenbergia)  the  function  is 
probably  performed  by  certain  large  but  otherwise  undifferentiated 
cells  of  the  epidermis,  which  may  be  regarded  as  undeveloped  bulli- 
form cells. 

The  stomata  lie  near  the  bottom  of  deep  longitudinal  furrows  and 
usually  occur  more  abundantly  on  the  protected  ventral  surface  of  the 
leaf,  but  in  Chloris  petraea  only  on  the  dorsal  surface.  The  walls  of 
these  furrows,  in  Muhlenbergia,  Uniola,  and  Spartina  patens,  are  lined 
with  unicellular,  simple,  prickle-like  hairs,  which  doubtless  hinder  the 
escape  of  moist  air. 

Subepidermal  groups  of  stereome  occur  in  the  leaves  of  all  the 
grasses  and  in  the  margins  of  all  except  the  Muhlenbergia.  In  this 
great  development  of  strengthening  tissue  we  have  in  all  probability  a 
protection  against  the  mechanical  effects  of  the  wind,  to  which  strand 
grasses  are  much  exposed. 

The  chlorophyll  tissue  is  in  every  case  radially  arranged  in  single 
layers  around  or  at  each  side  of  each  mestome  bundle.  In  most  cases 
the  adjacent  cells  of  the  parenchyma  sheath  also  contain  chlorophyll. 

Each  mestome  bundle  is  surrounded  by  a  mestome  sheath  in  all  the 
species  except  Uniola  and  Muhlenhergia,  and  this  by  a  large-celled 
parenchyma  sheath.  The  parenchyma  sheath  without  the  mestome 
sheath  occurs  in  Muhlenbergia. 

Among  the  species  of  the  salt  marsh  which  were  examined,  the 
isolateral  type  of  leaf  prevails,  Kostelefzkya  virginica  and  Lippia 
nodiflora  being  the  only  exceptions,  and  in  these  the  leaves  are  but 
imperfectly  bifacial.  In  Juncus  roemerianus  the  leaf  is  terete. 
Thick  leaves  are  also  the  rule  in  this  formation  class,  although  less 


TISSUES.  283 

strikingly  so  than  in  the  sand  strand,  because  of  the  lack,  of  hirge 
woody  j)lants;  and  the  thickened  leaf  is  usually  of  a  soft,  succulent 
character  rather  than  leathery.  A  majority  of  the  species  show  a 
conspicuously  thickened  cuticle,  which  is  strongly  wrinkl«Ml  in  7  out 
of  15  of  them  and  granular  or  warty  in  3  more. 

Corresponding  to  the  isolateral  structure  of  most  of  tlu-  Icax  <-s  we 
find  stomata  on  both  surfaces  in  12  si^ecies;  on  tho  whohi  circumfe'r- 
ence  of  the  terete  leaf  of  Ju)icusroeinerin?ii(.s;  confined  to  tlie  ventral 
or  upper  surface  only  in  SjKiriina  stricfa  und  BorrirliUt  frufescens. 
In  4  species  the  guard  cells  are  slightly  prominent,  in  7  level  with  tlie 
epidermis,  in  3  slightly  sunken,  in  1  {Spariirta  slricta)  situated  in*ar 
the  bottom  of  deep  furrows.  Hairs  occur  in  l)ut  5  species.  In  l5or- 
richia  alone  they  form  a  dense  covering,  nearly  every  epidermal  cell 
appearing  to  have  developed  a  iDluricellular,  thin-walled  liair  by 
tangential  division.  It  is  evident  that  we  have  in  this  case  an  admi- 
rable j)rotection  against  excessive  transpiration. 

Stereome  occurs  in  notable  quantity  only  in  the  leaves  of  SiKiriina 
stricta  and  Juncus  roemerianus.  In  both  it  is  subepidermal  as  well 
as  about  the  mestome  bundles.  Juncus  roemerianus  is  especially 
noteworthy  for  the  strong  development  of  both  peripheral  and  axial 
stereome  groups.  Ilj'podermal  collenchyma,  or  collenchyma-likc 
tissue,  occurs  opposite  the  veins  in  two-thirds  of  the  species  examined. 

The  chlorenchyma  is  homogeneous  in  all  but  '2  species,  and  in  1  of 
these,  Lippia  nodiflora,  the  differentiation  is  slight.  In  nearly  all 
the  si)ecies  it  consists  of  comj)acu  palisade,  interrui)ted  in  several 
cases  by  ducts  or  lacunes.  In  the  leaves  of  most  of  the  species  there 
are  only  2  layers  on  each  side  of  the  isolateral  leaf,  but  in  Ju7irus 
roemerianus  the  bands  of  Avell-developed  palisade  are  5  or  6  layers 
thick.  In  several  of  the  Comj)ositae,  all  decidedly  halophilous  species, 
the  ends  of  the  palisade  layers  where  they  abut  upon  the  midvein 
converge  toward  the  vein  and  appear  as  if  radiating  from  it.  This 
was  observed  in  Iva  frufescens,  Baccharis  halitnifolia,  and  Aster 
teiiuifolius,  and  may  occur  in  other  species.  The  significance  of  this 
arrangement  is  not  known.  It  is  cited  by  Warming^  as  a  lialophytic 
character.  SjKirtijia  stricta  agrees  in  the  arrangement  of  its  chlo- 
rophyll tissue,  as  in  other  respects,  with  the  sand-strand  grasses. 

Colorless  parenchjnna,  which  i^robably  serves  for  the  storage  of 
water,  is  present  in  greater  or  less  quantity  in  S  species,  occupying 
the  greater  part  of  the  interior  of  the  leaf  in  4,  while  occurring  only 
about  the  veins  in  the  others.  In  l>oiricliia,  which  is  one  of  the  most 
xerophytic  in  structure  of  all  the  salt-marsh  species,  this  tissue  is 
best  developed.     It  is  also  well  exemplified  in  'Tissa  marina. 

In  the  3  salt-marsh  inhabiting  monocotyledons  examined — Triylo- 
cliin  striata,  Sjoartina  stricta,  and  Juncus   roemerianus — each  mes- 

'  Halofyt-Stndier,  p.  S50. 


284  THE    PLANT    COVERING    OF    OCRACOKE    ISLAND. 

tome  bundle  is  i)rovided  with  a  well-marked  mestome  sheath  and, 
outside  that,  a  parenchyma  sheath. 

When  Ave  compare  the  species  belonging  to  the  two  formation 
classes,  sand-strand  and  salt-marsh,  we  find  that  a  majority  of  both 
have  several  characters  in  common,  all  of  which  are  distincth'  xero- 
phytic  and  are  usually  interpreted  as  protecting  the  leaf  against 
excessive  transpiration  as  well  as  the  effects  of  too  intense  light. 
These  are :  Thickened  leaves,  thickened  cuticle,  and  development  of 
the  chlorophyll  tissue  as  compact  palisade  on  the  most  exposed  sur- 
face or  surfaces. 

More  numerous,  however,  are  the  differential  characters.  The 
leaves  of  the  sand-strand  species  are  usually  bifacial,  with  stomata 
only  on  the  dorsal  surface  or,  if  on  both  surfaces,  protected  by  a  hairy 
covering  or  lying  in  deej)  furrows;  and  the  palisade  is  situated  on 
the  more  exposed  upper  or  ventral  side  of  the  leaf.  The  salt-marsh 
species,  on  the  other  hand,  have  mostly  isolateral  leaves,  vertical  or 
nearly  vertical  in  i^osition,  with  stomata  and  i)alisade  on  both  sur- 
faces, and  (with  one  exception)  lacking  the  dense  hairy  covering. 
Conformably,  the  most  common  grass  of  the  salt  marsh,  Spartina 
stricta,  otherwise  so  similar  in  leaf  structure  to  the  dune  form  of 
>S'.  patens,  has  no  hairs  lining  its  stomatal  furrows.  The  cuticle  is 
wrinkled  or  warty  in  many  more  salt-marsh  than  sand-strand  species. 
AVater-storage  i3arenchyma,  which  is  notably  developed  in  the  sand- 
strand  vegetation  onl^^  in  the  monocotyledons,  is  present  in  a  majority 
of  the  salt-marsh  plants  of  the  most  diverse  relationship. 

Corresponding  to  their  growth  in  usually  open  formation,  and  con- 
sequently greater  exposure  to  the  wind,  the  sand-strand  plants  show 
a  much  stronger  development  of  stereome  than  do  the  salt-marsh 
species.  On  the  other  hand,  the  latter  are  better  i^rovided  with  hypo- 
dermal  collenchyma,  or  coUenchymatic  tissue,  opposite  the  veins;  but 
this  ma}^  be  more  imiDortant  as  a  protection  against  loss  of  water 
than  as  a  mechanical  strengthening  tissue. 

It  should  be  emphasized  that  not  onl}^  the  peculiarities  common  to 
plants  of  the  two  formation  classes,  but  likewise  most  of  their  respec- 
tive differential  characters,  are  really  of  a  xerophytic  nature.^  In 
some  cases,  however,  a  different  means  has  been  employed  by  sand- 
strand  species  on  the  one  hand  and  by  salt-marsh  species  on  the 
other  to  secure  the  same  end — protection  against  excessive  transpi- 
ration and  the  harmful  action  of  too  intense  light. 

'  In  his  most  recent  paper  on  the  subject.  Warming  (Halofyt-Studier,  p.  235) 
writes:  "It  is  not  possible,  from  the  investigations  here  described,  to  draw  any 
clear  distinction  between  characters  which  are  truly  xerophj^tic  and  such  a 3  are 
truly  halopliytic,  if  any  really  exist."  Schimper  (Pflanzengeogr.,  p.  99)  also  holds 
that  halophytes  can  not  be  distinguished  as  a  class  from  xerophytes,  since  the 
principal  object'of  the  peculiarities  of  structure  observable  in  plants  growing  in 
saline  soil,  however  moist,  is  the  reduction  of  transpiration,  just  as  it  is  in  plants 
snrrounded  by  a  physically  very  dry  soil  and  atmosphere. 


ANATOMY    OF    SAND-STRAND    SPECIES.  285 

SPECIES    OF    THE    SAND    STRAND. 
Panicum  AMARUM  Ell.^ 

Leaf  bifacial,  strongly  involute  when  dry,  midrib  not  prominent  on 
the  dorsal  surface  and  not  much  so  on  the  ventral  surface,  shjillow 
furrows  (deepest  each  side  of  the  midrib),  with  broad  and  rounded 
intervening  ridges  on  the  ventral  surface,  corresponding  to  very 
slight  depressions  on  the  dorsal  surface. 

Epidermis:  Ventral,  similar  to  the  dorsal,  but  willi  iliinner  outer 
cell  walls;  stomata  at  each  side  of  the  group  of  3  thick-\vall(Ml  1) uni- 
form cells  at  the  bottom  of  each  furrow;  hairs  none.  Dorsal  with  very 
thick,  porous  outer  cell  walls,  1  or  sometimes  2  short  cells  alternating 
with  long  ones,  except  in  the  rows  containing  stomata;  stomata  lying 
in  the  shallow  furrows,  with  walls  of  the  guard  cells  much  thickened; 
hairs  none. 

Subepidermal  stereome  in  large  groups  above  and  below  the  midrib, 
that  above  separated  from  the  hadrome  by  several  layers  of  thickish- 
walled,  colorless  parenchyma;  smaller  groups  above  and  below  the 
other  nerves;  strongly  developed  in  the  margins. 

Chlorophyll  tissue  (palisade)  arranged  radially  in  a  single  layer 
about  each  mestome  bundle,  almost  completely  encircling  the  smaller 
nerves,  interrupted  above  and  below  the  larger  ones,  each  2  neighbor- 
ing rows  of  palisade  separated  by  a  single  layer  of  colorless  paren- 
chyma; chloroi)hyll  likewise  occurring  in  the  cells  of  the  parenchyma 
sheath  which  adjoin  the  palisade. 

Mestome  bundles  surrounded  each  by  a  mestome  sheath  wliich,  in 
the  larger  veins,  has  all,  or  nearly  all,  of  its  cells  with  walls  (especially 
the  inner)  strongly  thickened ;  mestome  sheath  in  turn  surrounded 
by  a  large  celled  i^arenchyma  sheath;  mestome  parenchjnna  in  a  single 
layer  of  thick-walled  cells  sei^arating  the  hadrome  from  the  leptome. 

MUHLENBERGIA   FILIPE8   M.    A.    Curtis." 

Z/ea/(fig.  33)condui)licate  without  power  to  unfold,  appearing  as  if 
terete,  slightly  asymmetrical,  margins  almost  meeting  al)ove  the  mid- 
nerve,  and  hence  only  the  dorsal  surface  exposed.  From  ihe  sliuhi 
opening  between  the  margins  to  the  uiidrib  extends  a  narrow  iissui-e, 
with  lateral  furrows  between  the  larger  nerves  reaching  more  than 
halfway  to  the  dorsal  surface  of  the  leaf.  The  ridges  al)ove  the 
mestome  bundles  between  these  furrows  arc  broad  and  rounded  at 
apex,  except  that  of  the  midnerve,  which  is  narrowed  outward  (hence 
conical  in  cross  section).     On  the  dorsal  (outer)  surface  are  narrow, 

'The  typical  form  of  this  species  was  not  observed  upon  Ocracoke  JslaTid.  but 
the  leaf  of  var.  mi)iiLs  Vasey  &  Scribner,  which  was  collected  there,  c-orrespon«ls 
in  every  detail  to  that  of  the  type. 

-  Compare  Volkens's  figure  and  description  of  .lr/.s//f/</ t'///(//(t  (Fl.  vEi;ypt.,pp. 
49,  150,  t.  10,  ff.  4  to  7). 


286 


THE    PLANT    COVERING   OF    OCRACOKE    ISLAND. 


slit-like   furrows  between  each  2  nerves  (hence  2  to  every  ventral 
furrow),  opening  into  wider  air  spaces  with  stomata  at  each  side  of 

the  bottom.  Stomata  also  oc- 
cur near  the  bottom  of  the  ven- 
tral furrows,  but  are  there  less 
numerous. 

Epidermis:  Ventral  (fig.  34) 
with  cell  walls  thinner  than  on 
the  dorsal  surface,  many  of  the 
cells  extended  into  straight  or 
curved,  spreading,  unicellular 
hairs  which  line  the  main  cav- 
itj'  and  lateral  furrows  with 
a  dense  cross  work,  and  are 
larger,  thinner -walled,  and 
more  slender  than  those  which 
occur  on  the  dorsal  surface; 
bulliform  cells  none.  Dorsal 
(fig.  35)  with  smaller  cells,  the 
outer  Avail  and  cuticle  so 
greatl}^  thickened  as  nearly  to 
equal  the  cell  lumen,  the  areas  \ying  above  the  subepidermal  strands 
of  stereome  having  single  rows  of  short  cells  which  alternate  with 
several  rows  of  long  ones;  many  of  the  epidermal  cells  extended  into 
short,  stout,  pointed,  thick-walled,  unicellular,  appressed,  prickle- 
like hairs,  which  line  the  furrows. 

Subepidermal    stereome:    None    on    the 
ventral  side  of  the  leaf  and  in  the  margin; 


Fig 


-Muhlenbergia  fil ipes—triLnsYerse  section  of 
leaf.    Scale  75. 


'Fig.  ^.—MuhJenbergia  fiUpes— 
ventral  epidermis  of  leaf. 
Transverse  section,  showing 
the  hairs.  Beneath  the  epi- 
dermis are  layers  of  colorless 
parenchyma.     Scale  400. 


Fig.  35.-  Muhlenbergiafilipes— dorsal  part 
of  leaf  blade.  Transverse  section  show- 
ing the  epidermis  (Ep.),  stereome  (St.^^ 
and  rather  thick- walled  colorless  paren- 
chyma (Pa.),  which  borders  on  the 
mestome  bundle.     Scale  400. 


on   the   dorsal   side   in   the   form   of   flattened    supporting   strands^ 
beneath   the   mestome   bundles,   passing   gradualh'   into   the    often 


^"  Abgeplattete  Trager,"  Schwendener,  Mechan.  Princ,  p.  40. 


ANATOMY    OF    MUHLENBERGIA. 


287 


separates  it  tVom  ili 


lliick-walled,  colorless  parenchyma  wliicli 
tome  sheath. 

Clilorenchyma  (fig.  3G)  consisting  of  small,  branched  cells  wiih  smal 


i-adially  arraii,Li<'<l  ahout  racli 


-Zy^n/. 


_^  Too. 

Fig.  36.—Muhlenbergia  filipes— portion  of 
mestome  bundle.  Transverse  section 
of  blade,  showing  a  part  of  the  leptome 
(Lept.),  the  parenchyma  sheath  (P), 
the  chloreuchyma  (Mes.  Kand  the  col- 
orless parenchyma  (Pa.)  between  the 
mestome  bundles.    Scale  OUO. 


intercellular  spaces  in  a  single  layev 
mestome  bundle,  Ij'ing  only  at  the  sides 
of  the  larger  bundles,  but  extending 
in  horseshoe  form  around  the  ventral 
(hadrome)  portion  of  the  smaller  ones. 
Parenchyma  sheath  of  the  mestome 
bundles,  where  adjoining  cliloren- 
chyma, also  containing  chlorophyll. 

Colorless  parenchyma  (fig.  86)  occu- 
pying the  larger  ventral  ridges  (over 
the  larger  mestome  bundles),  and  in  2 
or  3  rows  of  cells  between  each  2  nerves, 
extending  from  the  ventral  to  the  dor- 
sal furrows.  Also  in  1  or  2  rows  sepa- 
rating the  chloreuchyma  from  the  pa- 
renchyma sheath  of  the  smaller  bun- 
dles. 

Mestome  bundles  (fig.  36)  with  a  large- 
celled  parenchyma  sheath;  mestome 
sheath  none,  but  mestome  parenchyma 
with  cell  walls  (especially  the  inner)  much  thickened,  surrounding  tlie 
larger  nerves,  simulating  a  mestome  sheath;  many  of  the  companion 
cells  in  the  leptome  very  thick- walled.^ 

'  The  two  species  of  Muhlenbergia  most  nearly  allied  to  31.  filipes  are  J/,  capil- 
laris  (Michx.)  Kuntli  and  M,  tricUopodea  (Ell.)  Chapm.  Chapman  regards  .1/. 
filipes  as  a  variety  of  M.  capillaris,  but  the  striking  histological  differences,  together 
with  good  morphological  characters,  show  that  in  M.  filipes  we  have  a  perfectly 
valid  species. 

A  comparison  of  the  leaf  anatomy  of  the  three  forms  gives  some  very  interesting 
results: 

(a)  M.  capillaris  is  a  plant  of  dry  sandy  or  rocky  (eugeogenous)  soils,  but  the  leaf 
shows  only  feebly  the  strong xerophy tic  structure  of  21.  filipes.  Material  from  (  t reat 
Falls,  Md. ,  was  studied.  Leaf  thinner  than  in  M.  filipes,  conduplicate  when  dry,  but 
flat  when  well  supplied  with  water.  Ventral  face  not  furrowed,  furrows  on  the 
dorsal  face  extending  nearly  halfway  through  the  leaf,  with  stomata  at  bottom. 

Epideriiiis  much  as  in  M.  filipes,  but  with  bulliform  cells  between  each  'J  nerves; 
hairs  much  fewer  than  in  filipes,  all  short,  thick- walled,  pointed,  and  prickle-like, 
occurring  on  the  ventral  face  only  above  the  nerves,  on  the  dorsal  face  lining  the 
stomata-bearing  furrows  and  there  thicker- walled,  with  hardly  perceptible  lumen. 

Subepidermal  sfereome  in  flattened  supporting  strands  al)ove  and  below  rhe 
mestome  bundles,  from  which  they  are  separated  by  thickish-walled,  colorless 
parenchyma;  and  also  in  the  leaf  margins. 

Chloreuchyma  as  in  filipes,  but  entirely  surrounding  the  smaller  bundles,  inter- 
rupted by  colorless  parenchyma  above  and  below  the  larger  (mes.  Also  much 
chlorophyll  in  the  cells  of  the  parenchyma  sheath  which  adjoin  tiie  chlorenchyma, 

Mestome  bundles  with  no  true  mestome  sheath,  but  mostly  surrounded  by  a  sin- 


288 


THE    PLANT    COVERING    OF    OCRACOKE    ISLAND. 


Spartina  patens  (Ait.)  Muhl.^ 

Leaf  involute  when  dry,  deeply  furrowed  between  the  nerves  on 
the  ventral  face,  high,  broad,  rounded  ridges  separating  the  larger 

gle  row  of  mestome  parenchyma  with  cell  walls  thinner  than  vafiUpes  and  evenly 
thickened;  mestome  parenchyma  aJso  in  a  single  layer  between  hadrome  and  lep- 
tome,  and,  with  a  few  of  the  companion  cells  of  the  leptome,  isolated  or  in  groups 
of  2  or  3,  very  thick- walled. 

(5)  Muhlenhergia  tricliopodes  is  a  plant  of  low,  often  moist,  pine  barrens  in  the 
Gulf  strip  of  the  Austroriparian  area.  The  example  here  described  was  collected 
in  Mississippi.  It  is  in  several  histological  characters  intermediate  between  capil- 
laris  ^-ndi  filixjes,  although  morphologically  the  most  distinct  of  the  8  species. 

Leaf  conduplicate  when  dry,  nearly  flat  when  supplied  with  abundant  moisture. 
Ventral  surface  with  only  the  2  or  3  nerves  nearest  each  margin  prominent  and 
separated  by  deep  furrows,  the  otliers,  including  the  midnerve,  barely  i)rojecting. 
Dorsal  surface  with  narrow  and  rather  deep  furrows  between  the  nerves. 

Epidermis:  Ventral  with  sing'e  rows  of  short  cells  alternating  with  several  rows 
of  long  ones;  hairs,  chiefly  in  the  furrows,  shorter,  stouter,  and  thicker- walled  than 
iufilipes;  bulliform  cells  much  as  in  capillaris,  rather  thick- walled.  Dorsal  with 
rather  thick- walled  cells  (less  so  than  in^Zipes),  single,  quadrangular  (from  above), 
short  ones  alternating  with  longer  ones;  hairs  short,  stout,  thick-walled,  prickle-like. 

Suhepidermal  stereome  rather  more  strongly  developed  than  in  capillaris  and 
jilipes,  in  flattened  supports  above  and  below  the  mestome  bundles  (hence  at 
summit  of  the  ventral  ridges),  strongest  on  the  dorsal  side,  where  it  interrupts 
the  parenchyma  sheath  of  the  larger  nerves:  also  in  the  margins. 

Clilorencliyma  with  cells  as  in  filipes,  radially  arranged  in  single  layers  about 
the  bundles,  entirely  encircling  the  smaller  ones,  in  the  larger  ones  perpendicular 
to  the  leaf  surface  and  extending  to  the  stereome  at  the  summits  of  the  ventral 
ridges  (as  in  Spartina  strict  a  and  Uniola  panicidata)-,  parenchyma  sheath  and 
the  large  parenchyma  cells  above  the  mestome  bundles  also  containing  chlorophyll 
where  they  adjoin  the  smaller-celled  chlorenchyma. 

Colorless  parenchyma  (rather  thick- walled)  filling  the  interior  of  the  ridges,  and 
in  a  single  row  of  large  cells  between  each  2  nerves,  separating  their  respective 
bands  of  chlorenchyma. 

Mestome  bundles  withont  a  true  mestome  sheath,  but  the  larger  ones  surrounded 
by  a  layer  of  mestome  parenchyma  which  is  much  thicker-walled  than  in  the  2 
related  species;  around  the  smaller  bundles  the  mestome  parenchyma  thinner- 
walled  and  interrupted  by  2  large  vessels  of  the  hadrome;  mestome  parenchyma 
also  in  t  layer  between  hadrome  and  leptome,  as  in  the  other  2  species. 

The  important  leaf  characters  of  these  allied  species  of  Muhlenhergia  may  be 
tabulated  thus; 

[The  sign  x  indicates  presence  of  character.] 


Species. 

1 

It 

1 

3 

^1 

tc.5 

p. 

1 

6 

|.3 

i1 

II,. 

a  o 

m 

ii  lii 

1 

1 

^1 

a® 

o  > 

p. 

?2 

u 

13 

s 

«2 

2  H 

s 

p 

3  o  s  -:;  c  c 

^^J-^^    z>  a-^^ 

P 

< 

Q 

« 

^•-^ 

S 

ffl 

ffl 

^ 

02 

^     ,^ 

Cai3illaris 

X 

X 

X 

X 
X 

X 
X 

X 
X 

■       1    X 

Trichopodes 

X 

X     1 

X 

X 

X 

X 

I 

'  Compare  the  figure  of  S.  versicolor  in  Duval- Jouve,  Etude  Anat.,  ^>/.  lC,jhj. 


ANATOMY    OF    SPARTIXA.  289 

fill-rows,  which  aw  L'-clcrt  at  l)<)ll(nii  hy  Ili<'  low  i-idges  of  lli«*  siiiallc 
nerves. 

EpiderDiis:  Ventral  willi  cells  much  smallrr  and  riiinn<'r-wallc<i 
than  on  the  dorsal  surface;  stoniala  on  <'ach  side  of  the  bottom  of 
tlie  furrows,  somewhat  ijrominent;  many  of  the  epidermal  cells 
extended  into  short,  rather  thin-walled,  erect,  unicellular  i)ai)illae 
with  broad,  rounded  or  truncate  summits,  and,  especially  at  tlio 
summit  of  the  ridges,  into  longer,  sharp-pointed,  thick-wuUed,  erect, 
piickle-like  hairs;  typical  bnlliform  cells  nom,',  1  nit  at  the  bottom  of 
each  furrow  a  gronp  of  nsually  3  large  epidermis  cells,  which  are 
probably  functionally  homologous.  Dorsal  with  tliic'k,  porous  walls, 
which,  in  the  rows  containing  stoniata,  are  unevenl}^  thickened  so  as 
to  appear  wavy,  1  or  more  often  2  short  cells  alternating  with  the 
longer  ones;  cuticle  thick;  stomata  in  very  shallow  furrows;  hairs 
and  pai^illae  none. 

Suhepidernial  stereome  not  as  strongly  developed  as  in  most  of  the 
strand  grasses,  in  small  grou^Ds  on  the  dorsal  side  of  each  nerve;  in 
flattened  sufjporting  strands  at  the  summit  of  each  ventral  rib  and 
extending  some  distance  down  its  sides;  and  in  comparatively  small 
strands  in  the  leaf  margins. 

Chlorophyll  chiefly  in  the  j)arenchyma  sheath  of  the  mestonn^  Inin- 
dles,  Avith  a  "bridge"  of  small-celled  chlorenchyina  connecting  each 
two  neighboring  sheaths;  palisade  none. 

Colorless  parencliyma  filling  the  ventral  ribs  abov<^  the  mestome 
bundles  where  it  interrupts  the  ijarenchyma  sheath,  a  few  cells  also 
interrui^ting  the  parenchyma  sheath  on  the  dorsal  side. 

Mestome  bundles  surrounded  l)y  a  mestome  sheath  whose  walls 
(esi)ecially  the  inner)  are  much  thickened  only  on  the  leptonui  side 
of  the  larger  nerves;  parenchyma  sheath  (enveloping  tlie  mestome 
sheath)  containing  chlorophjdl,  continuous  about  the  smaller  nerves, 
interrupted  by  colorless  i^arenchyma  above  and  l)elow  the  larger  ones; 
mestome  i)arenchyina  (thick- walled)  in  a  single  layer  between  the  lep- 
tome  and  the  hadrome  of  the  larger  bundles. 

Spartina  stricta  (Ait.)  Koth.' 

Leaf  conduplicate  when  dry,  not  furrowed  on  the  dorsal  surface, 
deei)ly  furrowed  on  the  ventral  side,  the  funows  aciii*-,  I  lie  inter- 
vening ridges  broad  and  truncate  at  summit. 

Epidermis:  Ventral  with  cells  nari'owci-  and  not  s<>  liigli  as  on 
the  dorsal  surface,  the  walls  as  in  .S'.  jxdcns^  except  that  the  outer 
wall  of  each  cell  is  covered  with  silicilied  papillae;  stomata  on  eacli 
side  of  tlu^  bottom  of  the  furrows;  hairs  none;  typical  bulliform  <'ells 
none,  but  1  to  3  epidermal  cells  at  bottom  of  each  Ncntral  furrow 
somewhat  larger  than  the  others  and  probably  functioning  as  bulli- 

'  Although  this  species  belon-^'s  to  the  salt  marsh,  it  is  described  liere  for  the 
sake  of  convenient  comparison  with  theoth  rGram  neae.    Compare  Duval-.Touve, 
Histotaxie,  pi.  .18,  jig.  r>.    The  Ocr  icoke  plant  is  nearly  o£  the  typical  form. 
2965 3 


290 


THE    PLANT    COVERING    OF    OCRACOKE    ISLAND. 


form  cells.  Dorsal  as  in  S.  patens,  the  short  cells  iisuall}'  single, 
here  and  there  rounded,  with  strongly  thickened  walls,  almost  form- 
ing papillae;  stomata  none;  hairs  none. 

Hypoclermial  colorless  parenchyma  in  a  single  la^^er  beneath  the 
dorsal  epidermis,^  interrupted  hy  subepidermal  stereome. 

Stereome  not  strongly  developed,  a  small  subepidermal  group  on 
the  dorsal  side  of  each  mestome  bundle;  flattened  supporting  strands 
(1  or  2  la^^ers)  at  the  summit  of  each  ventral  ridge,  not  decurrent 
along  its  sides;  also  in  the  leaf  margins. 

ChloreiicJiyma  consisting  of  small  palisade  cells  in  a  single  laj^er, 
radially  arranged  on  each  side  of  each  mestome  bundle  and  extend- 
ing immediately  beneath  the  epidermis  to  the  stereome  at  the  summit 
of  each  ventral  ridge ;  each  2  neighboring  laA^ers  of  palisade,  between 
each  two  nerves,  either  adjoining  or  separated  by  a  few,  large,  color- 
less iDarenchyma  cells;  chlorophyll  also  in  most  of  the  cells  of  the 
parenchyma  sheath. 

Mestome  bundles  with  mestome  sheath  and  mestome  parenchyma 
much  as  in  S.  p)atens.  Parenchyma  sheath  (around  the  mestome 
sheath)  of  large  cells,  those  adjoining  the  palisade  laj^er  containing 
chloroi)hyll,  the  sheath  occasionally  interrupted  on  the  dorsal  side  of 

the  bundle  by  a  few 
cells  of  the  subepider- 
mal stereome.  Large 
parenchj^ma  cells,  in  2 
or  3  laj^ers,  occup3dng 
the  thickness  of  the 
ventral  ridges  and  ap- 
pearing to  be  an  exten- 
sion of  the  paren- 
chyma sheath;  when 
in  3  layers,  the  middle 
one  colorless.^ 


YiQ.^l.—Chloris 2^etraea—\ea,f.  blade.  Transverse  section. show- 
ing the  midrib  in  the  keel,  covered  by  layers  of  colorless  tis- 
sue and  a  group  of  buUiform  cells  (BC)  on  the  ventral  sur- 
face; be,  a  small  group  of  bulliform  cells  between  two  mestome 
bundles.  The  mestome  bundles  are  indicated  by  their  paren- 
chyma sheaths  and  by  the  stereome,  which  forms  small  sub- 
epidermal groups.  The  thick  walled  mestome  sheath  is  drawn 
only  in  the  two  large  bundles.    Scale  84. 


Chlorispetraea  Sw.^ 

Leaf  (fig.  37)  becom- 
ing conduplicate  AAiien 


^The  specimen  figured  by  Duval-Jouve.  loc.cit.,  ha.s  3  or  3  layers. 

'-Spartina  stricfa  mariiima  (Walt.)  Scribn.,  the  common  form  elsewhere  along 
our  Atlantic  coast,  is  prat^tically  identical  in  leaf  anatomy  with  S.  strictd  from 
Ocracoke,  except  in  the  following  particulars:  The  epidermis  cell  walls  on  the 
dorsal  surface  are  thinner  and  less  porous  and  show  less  of  the  wavy  thicken- 
ing: the  short  cells  are  more  often  in  pairs,  and,  when  single,  are  more  often 
papilliform;  stereome  is  somewhat  more  strongly  developed,  as  would  be  expected 
from  the  larger  size  of  the  plant  and  the  greater  length  of  the  leaves.  The  mate- 
rial examined  was  from  Lynnhaven  Bay,  Virginia. 

'Figured  by  Duval-Jouve,  Histotaxie,  p.  35o,  pi.  IS,  f.  1.  For  an  example  of 
similar  leaf  structure  compare  the  same  nuthor's  paper.  "Etude  histotaxifjue  des 
Cyperus  de  France,"  Mem.  de  I'Acad.  de  Montpellier,  tome  1  pL  22,  f.  6.     1874, 


ANATOMY  OF  CHLORIS  PETKAEA. 


291 


us 


md  slii(litly  inii)ivssed  veii- 
mestome  bundle  nt  tho  aj)ox 
keel.     Hairs  none. 

hiilliforin   cells    in   a    iaih(M' 


-5"*.. 


Fig.  d8.—Chlnris])etruea— ventral  portion  of  leaf  blade. 
Transverse  section,  showing  epidermis  (£/>)  and 
subepidermal  stereome  (St);  at  M  the  me.stome 
sheath  of  a  bundle,  bordering  on  layers  of  colorless 
parenchyma.     Scale  240. 


dry,  strongly  keeled  on  tiie  dorsal  face 
trally  opposite  the  niidvein,  with  a  large 
of  and  3  smaller  ones  on  each  side  of  th( 

Epidermis:  Ventral,  differentiated 
wide  band  above  the  keel  and 
in  2  small  groups  of  al)Out  4 
cells  each,  1  between  the  first 
pair  of  nerves  on  each  side  of 
the  keel;  elsewhere  plurieellu- 
lar  (3  or  4  layers)  and  occu- 
pying more  than  one-half  of 
the  thickness  of  the  leaf,  ex- 
cept above  the  larger  nerves, 
thin-walled  (excei^t  the  outer 
wall  of  the  outermost  layer) 
and  large  (except  the  single 
outermost  la3^er  where  it  lies 
above  the  subepidermal  groups  of  stereome) ;  stomata  none.  Dorsal 
epidermis  one-layered,  with  cells  all  small,  the  outer  wall  and  cuticle 
much  thickened,  radial  walls  thin,  undulate,  one  row  of  short  cells 
with  strongly  silicified  walls  alternating  with  several  rows  of  long  ones, 
many  of  the  cells  developed   into  rounded,  not   silicified,  papillae; 

stomata  in  the  strips  of  epi- 
dermis which  lie  between 
the  nerves,  level  with  the 
epidermal  surface. 

Subepidermal  stereome 
(fig.  38)  in  flattened  sup- 
ports above  and  1)elow  the 
mestome  bundles,  that  on 
the  ventral  side  in  1  or  2 
layers  above  the  lai-ger 
nerves,  reduced  to  small 
groups  (sometimes  only  2 
cells)  above  the  smaller 
ones;  on  the  dorsal  side 
supports  stronger,  some- 
times 3-layered;  also  in 
the  leaf  margins. 

Chlorencli y /// a ,  pa  1  i sade, 
arranged  radially  in  a  sin- 
gle row  of  cells  on  each 
side  of  each  mestome  l)undle,  with  a  "l)ri(lge"  of  small-celle<l  ehlo- 
renchyma,  containing  usually  a  few  cells  of  colorless  parenchyma, 
connecting  each  2  neighboring  i-ows;  chlor<)])hylI  likewise  in  Hie 
parenchyma  sheath  where  it  adjoins  the  palisade. 


Fig.  39.— CIdoris  j^etraea— large  mestome  bundle  from  leaf 
blade.  St,  stereome  of  lower  face  of  blade,  bordering  on 
the  mestome  sheath  (M),  which  encircles  both  tlie  lep- 
tome  and  hadrome  as  a  closed  sheath  of  thick-walled, 
porous  cells.  Bordering  on  the  mestome  sheath  is  a 
green  parenchyma  sheath  (P).  VV,  vessels;  L,  lacuno 
with  an  annular  vessel.     Scale  560. 


292 


THE    PLANT    COVERING    OF    OCRACOKE    ISLAND. 


Mestome  bundles  each  inclosed  by  a  mestome  sheath  (figs.  38,  39,  40) 
which  has  small  cells  with  equally  thickened  walls;  parenchyma 
sheath  with  large,  thin-walled  cells  containing  chlorophyll  where  they 
adjoin  the  palisade;  mestome  parenchyma  in  a  single  layer  sepa- 
rating the  hadrome  from  the  leptome  of  the  larger  bundles;  com- 
panion cells  of  the  sieve  tubes  with  much  thickened  walls. 


..P 


Fig.  40.—C'hloris  j^etraea— three  small  mestome  bundles  from  the  blade.  (Letters  as  in  fig.  39.) 
In  a  the  mestome  sheath  is  thick- walled  only  on  the  leptome  side;  in  6  and  c  the  thickening  of 
the  mestome  sheath  is  more  distinct  and  begins  to  show  also  on  the  hadrome  side.  The  sheath 
is  closed  in  all  of  these  small  bundles  and  is  a  true  mestome  sheath.    Scale  560. 

Uniola  paniculata  L.^ 

Leaf  rather  thick  and  hard,  more  or  less  involute  when  dry,  deeply 
furrowed  on  the  ventral  surface,  the  intervening  ridges  broad  and 
truncate  or  but  slightly  rounded  at  summit;  dorsal  surface  with  very 
slight  corresponding  depressions. 

Epidermis:  Ventral  with  cells  smaller  and  thinner-walled  than  on 
the  dorsal  surface,  the  outer  w^alls  more  arched,  many  of  the  cells,  espe- 
cially on  the  sides  of  the  furrows,  extended  into  short,  stout,  pointed, 
unicellular,  antrorse,  prickle-like  hairs  with  cuticle  rough  and  exces- 
sively thickened  (lumen  almost  obliterated  except  toward  the  base) ; 
stomata  near  the  bottom  of  the  ventral  furrows;  bulliform  cells  in  very 
small  groups  at  the  bottom  of  the  furrows.  Dorsal  with  conspicuously 
pitted  walls  and  ver^^  thick,^  strongl}^  wrinkled  cuticle,  1  or  sometimes 
2  or  3  short  cells  alternating  in  the  same  rows  with  long  ones ;  hairs 
none;  stomata  less  numerous  than  on  ventral  surface. 

Stereome  strongly  developed  (more  so  than  in  any  other  of  these 
strand  grasses) ;  strong,  flattened  subepidermal  supports  at  the  sum- 
mits of  the  ventral  ridges,  separated  from  the  mestome  bundles  by 
thin-walled  colorless  parenchyma  which  also  contains  small,  isolated 
groups  of  stereome;  narrow,  mostly  2-layered  subepidermal  groups 
on  the  dorsal  side  opposite  the  ventral  furrows;  strong  subepidermal 
supports  on  the  dorsal  side  of  each  mestome  bundle;  finallj^,  strong 
marginal  groups. 

Chlorenchyma:  Palisade  small-celled,  radially  disposed  on  each  side 
of  each  mestome  bundle  in  single  layers,  which  are  perpendicular  to 


'  Compare  Holm,  Bot.  Gaz.  vol.  16,  p/.  32,  ff.  8  to  12,  1891. 

2  But  much  less  so  than  in  Holm's  material  from  Fort  Monroe,  Va, 


ANATOMY    OF    YUCCA. 


293 


the  leaf  surface  and  extend  nearly  to  the  suniniit  of  the  ventral  ridges; 
inside  the  layer  of  j)alisade,  and  parallel  to  it,  is  a  single  layer  of  large, 
thin-walled  parenchyma  cells  containing  chloroph}'!!,  which  represents 
an  inii^erfect  i^arenchyma  sheath  to  the  mestonie  ])undles. 

Colorless  parenchyma  in  several  layers  which  lie  below  the  xmii-al 
furrows  and  separate  each  two  neighboring  layers  of  palisado. 

Mestome  bundles  without  a  true  niestome  sheath,  but  willi  Urn  lep- 
tome  sui-rounded  by  an  unbroken  ring  of  mes- 
tome parenchyma  having  small  cells  with  thick 
porous  walls. 

Yucca  aloifolia  L. 

Leaf  isolateral,  thick,  especially  toward  the 
base,  ending  in  a  rigid  apical  spine. 

Epidermis  (figs.  41,  42)  ceils  containing  chlo- 
rophyll, mostly  somewhat  elongated  parallel  to 
tlie  leaf  axis,  their  walls,  especially  the  arched 
outer  ones,  greatly  thickened  and,  together  with 
the miassive cuticle,  exceeding  the  celllumen,  the 
radial  walls  not  undulate;  cuticle  sharpl}^  differ- 
entiated, beautifully  stratified,  divided  b}^  per- 
pendicular lamellsB  corresponding  to  the  radial  cell  walls;  stomata 
deeply  sunken,  lying  beneath  the  cuticle  at  the  bottom  of  urn-shaped 
passages  whose  outer  orifice  is  quadrangular  with  raised,  cushion-like 
borders,  the  ridges  of  exit  at  bottom  of  the  pore  very  acute;  papillae 
none  (perhaps  present  in  younger  leaves). 

Interior  of  the  leaf  occupied  by  homogeneous,  thin- walled  paren- 
chyma, which,  toward  the  apex  of  the  leaf,  contains  chlorophyll  in 
its  entire  thickness. 

Mestome  bundles  lying  in  several  rows  in  the  mesophjdl,  each  sur- 
rounded by  a  parenchyma  sheath. 

Stereome  in  massive  groups  on  both  tlie  lep- 
tome  and  the  hadrome  side  of  the  bundles,  espe- 
cially strong  on  the  hadrome  side.  Small  bun- 
dles of  stereome,  each  with  a  parenchyma  sheath, 
are  scattered  among  the  mestome  bundles. 

Yucca  gloriosa  L. 


Fig.  U.— Yucca  aloifolia  — 
leaf  surface.  Epidermis, 
showing  openings  lead- 
ing to  the  stomata.  Scale 
320. 


Fig.  i2.— Yucca  aloifolia- 
a  stoma.  Cross- section 
Scale  320. 


Leaf  much  like  the  preceding. 

Epidermis  with  larger  (higher)  cells;  dorsal 
surface  bearing  thick,  rounded,  1-celled  papilhe. 

Apical  spine  with  exceedingly  thick  outer  epidermis  walls  and 
cuticle,  these  much  higher  than  the  celllumen,  radial  and  inner  walls 
also  much  thickened;  next  a  hypodermal  layer  of  thick-walled  col- 
lenchyma;  then  1  or  2  layers  of  thick-walled  collencliy mafic  tissue; 
and,  finally,  a  dense  mass  of  stereome,  inclosing  a  small  central 
mestome  bundle. 


294  THE    PLANT    COVERING    OF    OCRACOKE    ISLAND. 

Myrica  carolinensis  Mill.^ 

Leaf  bifacial,  thickisli,  botli  surfaces  sprinkled  with  resiniferous 
glands,  appearing  to  the  unaided  eye  as  granules  of  resin. 

Epidermis:  Ventral,  cells  small,  radial  walls  not  undulate ;  cuticle 
thick,  smooth;  stomata  none;  long,  pointed,  unicellular  hairs  with 
thick- walled,  smooth  cuticle  scattered  along  the  veins;  short-stalked, 
suj^erficially  flat,  scale-like,  pluricellular  glands  occupying  deep 
depressions  but  usually  rising  above  the  level  of  the  epidermis,  these 
filled  with  a  mass  of  bright-yellow  resin  which  breaks  down  the  cell 
walls  and  finally  itself  disorganizes,  the  stalk  of  each  gland  radially 
surrounded  by  numerous  small  foot  cells.  Dorsal  similar,  but  cuticle 
less  thickened,  glands  less  numerous,  and  stomata  present,  lying  in 
all  directions,  each  surrounded  by  5  to  7  ordinary  epidermis  cells,  the 
guard  cells  slightly  prominent. 

Chlorencliyma  sharply  differentiated  into  one  very  compact  layer 
of  i)alisade  with  high,  narrow  cells,  and  several  layers  of  open  pneu- 
matic tissue  with  rather  large  intercellular  spaces. 

Colorless  thin-walled  parenchyma  in  narrow  plates  interrupting  the 
chlorenchyma  above  and  below  the  smaller  vein^. 

Hypodermal  collenchymatic  tissue,  thick-walled,  in  2  or  3  layers 
above  and  below  the  midvein. 

Mestome  bundles  of  midvein  reinforced  by  stereome  which  adjoins 
both  the  hadrome  and  the  leptome,  that  below  the  leptome  separated 
from  the  hypodermal  collenchymatic  tissue  by  a  little  thin-walled 
parenchyma. 

Myrica  cerifera  L. 

Leaf  usuall}^  somewhat  thinner  than  in  M.  carolinensis. 
Epidermis  similar,  but  with  fewer  hairs  along  the  veins. 
Palisade  somewhat  thicker,  in  2  layers  of  lower  cells. 

QUERCUS   VIRGINIANA   L.^ 

Leaf  persistent,  thick,  bifacial,  upper  surface  shining,  margins 
sometimes  revolute,  veins,  especially  the  midvein,  prominent  beneath. 

Epidermis:  Ventral  with  nonundulate  cell  walls,  the  outer,  espe- 
cially,  strongly  thickened ;  cuticle  thick,  smooth;  stomata  none;  hairs 
none.  Dorsal,  cell  walls  as  on  the  ventral  surface ;  stomata  with  guard 
cells  slightly  i)rominent,  lying  in  all  directions,  each  bordered  by  sev- 
eral small  epidermis  cells;  hairs  (fig.  43)  forming  a  dense  covering, 
stellate,  consisting  of  8  to  18  acute,  thick-walled  unicellular  arms 
upon  very  narrow  foot  cells,  cohering  toward  their  bases  so  as  to  form 
a  saucer-shaped  scale. 


^  Material  examined  from  near  Norfolk,  Va. 

^Q.  virens  Ait.    Material  examined  was   from    near  Norfolk,  Va.      Compare 
Quercus  ilex  as  described  and  figured  by  Lalanne,  Recherches,  p.  3,  pL  7,  ff.  9,  ii. 


ANATOMY    OF    ZANTHOXYLUM    CLAVA-HERCULIS.  295 

Hyp(xlena  mostly  :3-hiyered,  colleneliyniatie,  continuous  on  \hA\\ 
surfaces  (rarely  interrupted  hy  palisade),  replacing  the  chloren- 
chyma  and  forming  thick  masses  above  and  especially  below  the 
mid  vein. 

Sfereome  thin-walled,  in  narrow  plates  interrupting  the  chloi-cn- 
chyma  and  extending  through  the  leaf  opposite  most  of  thr  smaller 
veins;  in  strong  masses  above  and  below  the  midvein. 

Chlorenchyma:  Palisade  compact,  mostly  in  2  layers,  passing  grad- 
ually into  pneumatic  tissue  of  which  only  the  low- 
est layer  is  comparatively  open  and  short-celled.^ 

ZANTHOXYLUM    CLAVA-HERCULIS   L.- 

Leaf  bifacial,  thickish,  dark  green  and  shining 
above. 

Epidermis:  Ventral,  cells  large,  walls  not  undu- 
late, the  outer  strongly  thickened,  the  others  thin; 
cuticle  sharply  defined,  delicately  wrinkled;  sto- 
mata  none ;  hairs  none.  Dorsal,  cells  smaller,  the 
outer  walls  and  cuticle  thinner ;  stomata  with  guard  a/ia-steiiate  hair  from 
cells  slightly  prominent,  lying  in  all  directions,  dorsal  leaf  surface. 
surrounded  by  4  to  6  epidermis  cells;  hairs  none,      scale m  ^^^ 

HypodeTmal  coUenchyma  with  strongly  thick- 
ened walls  in  4  or  5  narrow  laj^ers  above  the  midvein ;  coUenchymatic 
tissue  in  4  or  5  wide  layers  beneath  the  midvein. 

Chlorenchyma:  Palisade  a  single  compact  layer  of  short  cells; 
pneumatic  tissue  in  2  or  3  layers,  rather  open. 

Oil  reservoirs  schizolysigenous,^  scattered  through  the  mesophyll 
near  the  ventral  surface,  and  larger  ones  at  the  base  of  each  indenta- 
tion of  the  leaf  margin,  surrounded  by  2  or  3  layers  of  thickish- walled 
parenchyma  with  cells  strongly  compressed  parallel  to  the  surface  of 
the  cavity. 

Mestonie  bundles  surrounded  by  a  thin,  interrupted  sheath  of  stere- 
ome,  which  is  continuous  and  (in  cross  section)  crescent-shaped  out- 
side the  leptome. 

'  Quercus  laurifolia  Michx.  is  a  deciduous-leaved  species,  common  along  the 
coast  and  ijerhaps  occurring  upon  Ocracoke  Island.  Leaves  from  Cape  Henry, 
Va.,  show  the  following  differences  from  Q.  virginiana: 

Epidermis:  Cuticle  thicker;  dorsal  surface  less  densely  covered  with  similar 
stellate  hairs,  their  arms  longer,  more  slender  and  much  thinner- walled. 

Collencliymaticliypoderm  none  except  above  the  midvein.  True  coUenchyma 
(hypodermal)  strongly  developed  beneath  the  midvein. 

Stereome  entirely  surrounding  the  midvein,  ^vllere  it  is  much  thicker-walled 
than  in  virginiana. 

Chlorenchyma:  Only  the  uppermost  layer  typical  pahsade;  pneumatic  tissue 
more  compact  and  with  more  elongated  cells  than  in  civgtniana, 

-Material  from  Virginia  and  Mississippi. 

=*  Compare  Solereder,  Syst.  Anat.,  p.  '201. 


2^6 


THE    PLANT    COVERING    OF    OCRACOKE    ISLAND. 


Croton  maritimus  Walt. 

Leaf  flat,  bifacial,  both  surfaces  densely  covered  with  a  gray,  scale- 
like pubescence. 

Epidermis:  Ventral,  cells  small,  walls  not  undulate,  thin;  siomata 
vei-y  numerous,  guard  cells  level  with  the  epidermis,  each  stoma  sur- 
rounded b}^  4  epidermal  cells, 
of  which  2  are  differentiated 
as  crescent-shaped  subsidiary- 
cells  parallel  with  the  guard 
cells;  hairs  pluricellular,  stel- 
late, consisting  of  a  long  cylin- 
drical stalk  rising  above  the 
surface  and  composed  of  many 
smaU  cells  partlj^  of  subepi- 
dermal origin,  from  the  apical 
cell  of  Avhich  radiate  in  a 
nearly  horizontal  plane  nu- 
merous unicellular,  sharp- 
pointed  arms  with  thick, 
smooth  cuticle,  cohering  near 
their  bases  so  as  to  form  a  shal- 
low cup.  Dorsal,  similar ;  cu- 
ticle thickened  and  granular 


Fig.  44.  — Cro/o?i  maritimus— Yisiiv  from  dorsal  leaf 
surface,  o.  View  from  above;  &,  cross  section;  Ep, 
epidermis;  P,  palisade.    Scale  340. 


underneath  the  large  veins; 
stomata  about  equally  numerous;  hairs  (fig.  44)  with  less  numerous 
and  thinner-walled  arms. 

Hypoderin^  none,  except  beneath  the  large  veins,  where  several 
layers  of  thin- walled  collenchymatic  tissue  occur. 

Stereome,  none. 

Chlorenchyma:  Palisade  in  one  layer,  comi3act,  the  cells  elongated, 
interruiDted  onh^  by  thick-walled,  branching,  sclerotic  idioblasts; 
pneumatic  tissue  of  roundish  cells.  •* 

Ilex  vomitoria  Ait. 

Leaf  evergreen,  thick,  shining  and  dark  green  above,  bifacial. 

Epidermis:  Ventral,  cells  rather  high  (but  small  in  their  diameter 
parallel  to  the  leaf -surf  ace),  the  outer  wall  and  cuticle  much  thick- 
ened but  not  nearly  so  high  as  the  cell  lumen,  radial  walls  rather 
thin,  undulate;  cuticle  smooth;  stomata  none;  erect,  short,  stout, 
pointed,  often  curved,  prickle-like  unicellular  hairs  with  ver^^  thick 
walls  (lumen  almost  obliterated)  and  smooth  cuticle  along  the  mid- 
vein.*  Dorsal,  cells  smaller,  thicker- walled  (outer  wall  and  cuticle 
exceeding  the  cell  lumen  in  height),  the  radial  walls  nearly  straight, 
porous;  cuticle  Avrinkled;  stomata  very  numerous,  guard  cells  slightly 
depressed;  hairs,  none. 

'  This  specie*!  is,  therefore,  an  exception  to  the  rule  that  evergreen  leaves  have 
no  hairs  on  the  upper  or  ventral  surface.     (See  Lalanne,  p.  117.) 


ANATOMY    OF    TEUCRIUM    NASHII.  297 

Hijpoderinal  collenchymatic  tissue  in  a  single  ntirrow  Uiyer  abov« 
the  luidvein  (as  in  I.  opaca)  and  several  layers  beneath  the  raid  vein. 

Chlorenchyma:  Palisade  in  two  layers;  pneumatic  tissue  rather 
open  (more  so  than  in  I.  aquifolium  and  I.  opaca). 

Mestome  bundle  of  midvein  reinforced  by  a  narrow  group  of  stereom. 
below  the  leptome,  and  a  thinner- walled  gronp  above  the  hadromeJ 

Oenothera  humifusa  Nutt. 

Leaf  densely  silky-pubescent,  imperfectly  bifacial,  midvein  slight  l.\ 
impressed  above,  not  prominent  beneath. 

Epidermis  similar  on  both  surfaces,  cell  walls  not  undulate,  som<'- 
what  thickened,  especially  the  outer;  cuticle  smooth;  stomata  witli 
guard  cells  level  with  the  upper  surface,  slightly  prominent  beneath, 
the  majority  lying  parallel  to  the  veins,  but  many  irregular;  hairs 
densely  matted,  subappressed,  long,  sharp-pointed,  unicellular,  with 
thick,  granular  cuticle,  each  radially  surrounded  by  5  or  6  foot  cells. 

Hypodermal  collenchyma  in  2  narrow  layers  above  and  1  wide 
layer  beneath  the  midvein,  separated  from  the  mestome  above  and 
below  by  colorless  (water-storage?)  parenchyma. 

Stereome,  none. 

Chlorenchyma  not  sharply  differentiated;  palisade  containing  large 
cells  inclosing  raphides,  which  are  yet  more  abundant  in  the  other- 
wise rather  compact  pneumatic  tissue. 

Teucrium  NASHII  Kearney. ^ 

Leaf  normally  horizontal,  bifacial,  dark  green  above,  white-tomen- 
tous  beneath,  margins  (especially  in  young  leaves)  somewhat  revolute, 
veins  impressed  above,  prominent  and  reticulated  beneath. 

Epidermis:  Ventral,  cell  walls  thin,  the  lateral  not  undulate  or  but 
very  slightly  so;  cuticle  smooth;  stomata,  none;  hairs  scattered, 
mostly  3  or  4  celled,  thin-walled,  smooth,  slender,  very  sharp-pointed, 
strongly  bent  so  as  to  lie  nearly  parallel  to  the  surface,  surrounded 
radially  by  4  to  10  (most  frequently  6)  foot  cells.  Dorsal,  cell  walls 
more  undulate;  stomata  in  the  sheltered  interstices  between  the  pro- 
jecting veins,  with  guard  cells  slightly  prominent,  lying  in  all  direc- 
tions, usually  bordered  by  2  epidermal  cells  and  at  right  angles  to 
their  dividing  wall,  but  with  many  exceptions;  long-pointed  hairs 
forming  a  dense  covering;  also  very  numerous,  spherical,  sessile,  glan- 
dular hairs  Avith  roughened  cuticle. 

Hypodermal  collenchymatic  tissue  in  2  or  3  narrow  layers  above  and 

'Specimens  cultivatedTat  Washington,  D.  C,  differ  in  having  :3  layers  of  pali- 
sade, and  no  stereome  above  the  hadrome  of  the  midvein. 

•'Teucrium  cauadensc,  which  is  never,  to  my  knowledge,  a  strand  plant,  differs 
ohieflv  in  the  less  dense  hairy  covering  of  the  dorsal  leaf  surface  and  in  the  dis- 
tinct granular  roughening  of  the  cuticle  in  the  pointed,  as  well  as  the  glandular 
hairs. 


298 


THE    PLANT    COVERING    OF    OCRACOKE    ISLAND. 


1  wide  layer  beneatli  the  midvein,  the  latter  separated  from  the  lex)- 
tome  b}^  several  layers  of  colorless  parenchjnna. 
Stereome,  none. 

Chlorenchyma:  Palisade  a  single  laj^er  of  short  cells,  very  compact; 

pneumatic  tissue  occupying  the 
rest  of  the  leaf's  thickness,  also 
rather  compact. 

Physalis  viscosa  L. 

Leaf  flat,  thin,  imperfectly  bifa- 
cial, gray-canescent  or  green  (de- 
pending upon  the  amount  of 
pubescence).^ 

Epidermis  similar  on  both  faces, 
cell  walls  not  thick,  the  radial  un- 
dulate ;  cuticle  above  and  beneath 
the  veins  thick  and  warty;  stomata 
much  more  numerous  on  the  dorsal 
surface;  hairs  (fig.  45)  about 
equally  numerous  on  both  faces, 

Fig.  i5.— Physalis  viscosa— branched  hair  from    thiu-walled  with  granular  CUticle, 

leaf.   Scale  240.  cousisting  of  a  uuicellular  stalk 

bearing  3  or  4  (usually  3)  conical,  acute,  unicellular  or  sometimes 
bicellular  arms,  these  in  turn  sometimes  once-branched. 

Hypodermal  colleiichy matte  tissue  above  and  beneath  the  veins. 

Stereome^  none. 

Chlorenchyma:  Palisade  and  pneumatic  tissue  not  well  differen- 
tiated, both  compact. 

^  The  individuals  observed  upon  Ocracoke  Islaad  had  greener,  less  pubesceut 
leaves  than  at  Cape  Henry,  Va. 


ANATOMICAL    SUMMARY    OF    SAND-STRAND    SPECIES. 


299 


Leaf  anatomy  of  sand-strand  species. 
[The  sign  x  indicates  presenct  of  character  :  ±  its  imperfect  development.] 


Leaf. 

Epidermis. 

Cuticle 

(3 

h 
II 

3 
1 

i 

Species. 

■3 
1 

"2 

1 

1 

V 

> 

i 

a 

i 

0, 

H 

o 

1 

Pauicum  amarum 

X 
X 
X 
X 
X 
X 

X 
X 
X 
X 

X 
X 
X 
X 
X 
X 

X 
X 
X 
X 
X 
X 
X 
X 
X 
X 

x 

X 

X 

Muhlenbergia  tilipes 

Spartina  patens 

Spartina  stricta^ 

X 

Chloris  petraea 

X 

X 

Uniola  paniculata 

X 
X 
X 

X 

Yucca  aloif  olia 

X 
X 

Yucca  gloriosa 

Myrica  carolinensis 

X 

X 
X 
X 
X 
X 
X 
X 
X 

My  rica  cerif  era 

Quercus  virginiana 

X 
X 

Zanthoxylum  clava-herculis 

X 

Croton  maritimus 

± 

Ilex  vomitoria    

X 

X 

X 

X 

Oenothera  humif  usa 

Teucrium  nashii 

± 

X 

Physalis  viscosa 

X 

Epide 

rmis. 

Stomata. 

Species. 

i 

OQ 

1 

> 

1 

"a 

1 

a 

a 

s. 
I 

a 

t 

a 

1 

si 

I 

i 

n 

.11 

Panicum  amarum 

X 
X 
X 

X 
X 
X 
X 

X 

X 
X 
X 
X 
X 
X 
X 

Muhlenbergia  filipes 

Spartina  patens 

Spartina  stricta 

X 

Chloris  petraea 

X 

X 

Uniola  paniculata 

X 
X 
X 

X 

Yucca  aloifolia 

X 
X 

Yucca  gloriosa 

X 

X 

X 

Myrica  carolinensis 

X 
X 
X 
X 

X 
X 
X 
X 

Myrica  cerifera. 

Quercus  virginiana.. 

Zanthoxylum  clava-herculis 

Croton  maritimus 

X 

X 

Ilex  vomitoria 

X 

X 

Oenothera  humifusa 

X 

X 
X 

X 

X 

Teucrium  nashii 

X 

X 

Physalis  viscosa 

X 

1 

1 

1  Belongs  to  the  Salt  Marsh,  but  is  inserted  here  for  convenience  of  comparison  with  other 
Gramiueae. 


300 


THE    PLANT    COVERING    OF    OCRACOKE    ISLAND. 


Leaf  anatomy  of  sand-strand  species — Continued. 


Epidermis. 

Hypoder- 

mal  colleu- 

chyma  or 

collencby- 

matic  tissue. 

Hairs. 

Species. 

r 

in 

1- 
1 

3 

6 

a 

1 

1 

1 

111 

II 

2 

1 

T*nnir>mTi  amaTiTm 

Mulilenbergia  filipes . . . 

X 

X 
X 

X 
X 

X 

OViloritj  ■nptrflPfl 

X 

X 

X 

Viirr-n  nlnifnlia 

1 

Myrica  carolinensis 

Myrica  cerifera 

X 
X 

X 
X 

X 
X 
X 

X 
X 

^( 

X 
X 

X 
X 

X 

X 

X 

Zanthoxylum       clava- 
herculis 

X 
X 

X 
X 
X 

X 

X 

X 
X 
X 

X 

X 

TIptt  vnmitoria 

X 

X 
X 
X 

X 
X 

X 
X 
X 

Tf^nnvinm  TintiViii 

X 

Physalis  viscosa 

X 

Stereome. 

Chlorenchyma. 

Water  par- 
enchyma. 

Mestome 
bundles. 

Species. 

1 

1 

1 

i 

1 
a 

q-l 
1 

a 

o 

tn 

a^ 

^§ 
.a-Q 

:o 
< 

§ 

Oi 

a 

1 
1 

s 

f 

il 
ii 

Is 
il 

r 

il 

ill 

111 
IP 

III 

1 

.a=^ 

a  . 
®| 

Q 

i 

2 

0) 

1 

g 

X 
X 
X 
X 
X 
X 

X 

X 
X 
X 
X 
X 
X 
X 
X 

X 



X 

X 
X 
X 

X 

X 
X 
X 

X 

Muhlenbergia  fllipes . . . 

Spartina  patens 

Spartina  stricta 

Chloris  petraea . 

Uniola  paniculata 

Yucca  aloif  olia 

X 

X 

X 

X 
X 
X 
X 

_ 

X 
X 
X 

X 
X 

X 

X 

X 
X 
X 

X 

X 

X 
X 

X 

X 

X 

Mvrica  carolinensis 

X 
X 
X 

X 
X 
X 

X 
X 
X 

X 
X 

X 

X 
X 

Zanthoxylum       clava- 
herculis 

Ilex  vomitoria 

X 

X 

Teucrium  nashii 

X 

V 

+   !   V 

ANATOMY    OF    TRIGLOCHIN    AND    JUNCUS.  301 

SALT  MARSH   SPECIES. 
TRIGLOCHIN   STRIATA    Ruiz  tfc  PaV. 

iea/ isolaterul,  thickish. 

Epidermis  cells  with  noimndulMte  walls,  the?  outer  strongly  lliick- 
ened;  cuticle  thick,  granular;  stoniata  in  rows  parallel  to  the  nerves, 
level  with  the  surface,  each  bordered  by  4  epidermal  cells,  of  which  2 
are  subsidiary  and  resemble  the  guard  cells;  hairs  ncjiie. 

Stereome  none. 

Chlorenchyma:  Two  outer  layers  compact,  continftous  on  l)oth  sur- 
faces, not  imlisadic  excei)t  at  the  leaf  margins,  where  o  layers  of  i)ali- 
sade  occnr;  parenchyma  of  the  interior  of  the  leaf  containing  little 
chlorophyll,  interrnpted  by  lacunes. 

Mestome  hundles  imbedded  in  the  interioi-  x^arenchyma,  each  sur- 
rounded by  a  small-celled  mestome  sheath,  whose  inner  walls  are 
excessively  thickened  and  layered ;  this  surrounded  by  a  sheath  of 
large-celled,  colorless  parenchj^ma. 

Spartina  stricta  (Ait.)  Roth. 

Treated  for  comparison  among  sand-strand  grasses,  page  289. 

JuNCUS   ROEMERIANUS  Scheele. 

J/er// vertical,  terete,  sharp-pointed,  stem-like. 

Epidermis  cells  all  small,  quadrangular  (superficially),  regular, 
without  alternation  of  long  and  short  cells;  smaller  and  thicker- walled 
over  the  bands  of  chlorenchyma  than  over  those  of  subepidermal 
stereome,  the  outer  walls  much  thickened  and  porous;  stomata^  with 
guard  cells  level  with  the  oilier  epidermal  cells;  hairs  none. 

Stereome  (subepidermal)  alternating  with  the  chlorenchyma  in 
strong  groups,  which  in  cross  section  are  I-shaped.'^ 

Cldorencliyma  of  typical  long,  narrow  palisade  cells,  mostl}"  in  5  or 
6  layers. 

Mestome  hundles  arranged  in  several  concentric  circles,  com- 
pletely surrounded  hy  stereome  (which  is  particularly  strong  on  thc^ 
two  sides  parallel  to  the  leaf  surface),  the  whole  enveloi^ed  by  a 
beautifully  i-egular,  large-celled  parenchyma  sheath.  Within  the 
stereome  the  bundle  is  encircled  by  a  mestome  sheath  of  small,  thick 
walled*  cells.  The  outer  mestome  bundles,  with  the  colorless  pareii- 
ch3"ma  between,  form  a  continuous  ring,  unbroken  by  lacunes.  The 
inner  bundles  lie  in  tliin  longitudinal  plates  of  parenchyma,  wliich 
separate  large  lacunes.  Small  bundles  of  stereome,  each  surrounded 
by  a  i)arencli3nna  sheath,  also  occur  in  tlie  interior  of  the  leaf. 

Stem  differing  but  little  from  the  leaf;  difference  consisting  cliiefly 
in  the  presence  of  a  cortex  of  some  thickness,  and  in  llie  less  elon- 
gated chlorenchyma  cells. 

'Of  the  type  common  in  Jnncaceae,  Cyperaceae,  and  Gramineae. 

2  '*  I-formige  Trager  "'  of  fecliweudener. 


302  THE    PLANT    COVERING    OF    OCRACOKE    ISLAND. 

Sesuvium  maritimum  (Walt.)  B.S.P.^ 

Z/ea/ isolateral,  somewhat  succulent. 

Epidermis  cells  with  non undulate,  radial  walls,  the  outer  some- 
what thickened,  some  of  the  cells  much  larger  and  probably  serving 
for  water  storage;  cuticle  smooth;  stomata  Ij^ing  in  all  directions, 
guard  cells  level  with  the  epidermis,  each  stoma  bordered  by  3  to  0 
(usually  4  or  5)  undifferentiated  epidermis  cells;  hairs  none. 

Stereome  none. 

Chlorenchyma  homogeneous  and  occupying  the  entire  thickness  of 
the  leaf,  interrupted  by  large  intercellular  spaces,  which  lie  beneath 
the  large  (water- storage)  epidermal  cells. 

Mestome  bundles  with  a  small  group  of  collenchyma  on  the  leptome 
side. 

Stein:  Epidermis  with  cell  walls,  especially  the  outer,  strongly 
thickened.  Stereome  none.  Collenchyma  in  small  groups  above  the 
leptome  of  the  primary  mestome  bundles.  Cells  containing  crystal 
masses  in  the  pith  and  a  few  in  the  cortex. 

TissA  MARINA  (L.)  Britton.^ 


Leaf  isolateral,  hemicylindric,  furrowed,  margins  sparsely  ciliate, 
especially  toward  base. 
Epidermis  with  cells  somewhat  elongated  parallel  to  the  leaf  axis, 
the  radial  walls  strongly  undulate,  the  outer  walls 
slightly  thickened;  stomata  always  parallel  to  the 
leaf  axis,  guard  cells  slightly  prominent,  lying  usu- 
ally between  2  ordinary  epidermis  cells  and  at  right 
angles  to  their  dividing  wall,  but  sometimes  bordered 
b}^  3  cells;  hairs  (on  the  margins)  glandular  (fig.  46), 
capitate,  with  a  3  or  4  celled  stalk. 
FIG.  m.-Tissa  mar-       Stereome  none. 
^■na— glandular  hair        CMorenchyma  compact,  its  cells  not  elongated. 
Scale  240^   margin.        Colovless  parenchyma  (water  tissue)  constituting 

the  interior  mesophyll. 
MesUyme  bundle  of  the  midvein  small,  lying  deep  in  the  water  tissue, 
with  a  small  group  of  collench3ana  outside  the  leptome. 

Stem:  Epidermis  with  thick  outer  cell  walls  and  wrinkled  cuticle. 
Outer  cortex  separated  from  the  inner  by  an  unbroken,  2-la3^ered  ring 
of  stereome,  with  cell  walls  (especially  of  the  inner  layer)  compara- 
tively thin. 

^  Sesuvium  pentandr} nil  Ell. — Compare  Warming's  description  and  figure  of 
^.  portulacastrum,  Halofj^t  Studier.  pp.  180,  211. 
■^  Spergularia  salina  J.  and  C.  Presl. 


ANATOMY    OF    VINCETOXICLM    PALUSTRE.  303 

KOSTELETZKYA   VIRGINIC'A    (L.)    A.    (4r{iy. 

Ledfhi'Oixd  and  flat,  bifacial,  stellate-pubescent  on  l)(>th  surfaces. 

Ejjide/Diis  cells  with  iioiiundulate,  thin  walls,  except  above  and 
beh)\v  the  larger  veins,  wliere  the  cuticle  is  rather  thick  and  layered; 
stomata  witli  guard  cells  sliglitly  proiiiin(^nt,  more  numerous  on  tlie 
dorsal  surface;  hairs  stellate,  consisting  of  5  to  8  acute  unicellular 
arms  with  thick,  smooth  cuticle,  separate  nearly  or  quite  to  the  l)ase, 
each  from  a  narrow  foot  cell  in  the  epidermal  plane. 

Hypoderrtial  colleiichyma  strongly  developed  above  and  below  the 
larger  veins. 

Chlorerichyriia:  Palisade  1-layered;  pneumatic  tissue  with  numer- 
ous small  intercellular  spaces;  mucilage  cavities  distribut(Ml  in  the 
chlorenchyma. 

Mestome  bundles  almost  completely  surrounded  by  a  thin,  inter- 
rupted sheath  of  stereome,  which  is  most  strongly  developed  outside 

the  leptome. 

Ammania  koehnei  Britton. 

Leaf  ^at,  rather  thin,  aijproximately  isolateral. 

Epidermis:  Cells  with  radial  walls  strongl}^  undulate ;  all  the  walls 
thin,  except  above  and  below  the  larger  veins,  where  the  outer  walls 
are  considerably  thickened;  cuticle  smooth;  hairs  none;  stomata 
chiefly  parallel  with  the  veins,  but  some  irregular;  guard  cells  slightly 
prominent,  each  stoma  bordered  by  usually  4  undifferentiated  epi- 
dermal cells. 

Collencliyma  none. 

Stereome  none. 

Chlorenchyma  homogeneous,  not  imlisadic. 

ViNCETOXicUM  PALUSTRE  (Pursh)  .\.  Gray.^ 

Leaves  narrow,  sharply  reflexed  and  hanging  almost  vertically, 
imperfectly  isolateral. 

Epidermis:  Cell  walls  rather  thick,  not  undulate;  cuticle  wrinkled, 
especially  above  and  below  the  veins;  stomata  more  numerous  on  the 
ventral  surface,  level  with  the  epidermis,  each  bordered  by  4  or  (more 
often)  5  ordinary  epidermis  cells,  generally  parallel  with  the  leaf 
axis  on  the  ventral  surface,  very  irregularly  disposed,  often  at  right 
angles  to  the  axis  on  the  dorsal  surface;  hairs  none. 

Hypoderni  a  single,  narrow  layer,  only  above  the  midrib. 

Collenchyma  none. 

Stereome  none. 

Chlorenchyma  not  palisadic,  homogeneous  through  IIh'  l«'af.  bnl 
the  interior  containing  less  chlorophyll. 

Cells  contain iiKj  masses  of  crystals  (calcium  oxalate)  scattcicd  in 
the  chlorenchj^ma. 

Stem:  Epidermis  as  in  the  leaf. 


'  Seutera  inaritima  Decsne. 


304 


THE    PLANT    COVERING    OF    OCRACOKE    ISLAND. 


Hypoderm  continuous,  1-Ui3'ered.  Outer  cortex  with  rather  thick- 
walled  cells,  containing  chlorophyll;  inner  cortex  gradually  becoming 
thinner- walled  and  colorless. 

Stereome  in  a  concentric  band  of  isolated  groups,  lying  Inside  the 
middle  of  the  cortex. 

Lactiferous  ducts  few,  Ijang  just  outside  the  mestome  bundles. 

Mestows  hundles  bicoUateral, 
perileptomatic,  the  leptome  most 
strongly  developed  on  the  outer 
l^eriphery  of  the  hadrome. 

LiPPIA    NODIFLORA   Mx. 

Leaf^  imperfectly  bifacial,  usu- 
ally horizontal,  but  sometimes 
vertical. 

Epidermis  alike  on  both  sur- 
faces, cell  walls  thick,  not  undu- 
late; cuticle  wrinkled;  stomata 
(fig.  47)  lying  in  all  directions, 
guard  cells  almost  level  with  the 
ventral  surface,  slightly  depressed 
on  the  dorsal  surface,  each  stoma 
bordered  by  2  crescent-shaped, 
chlorophyll  -  holding,  subsidiary 
cells  which  are  usually  at  right 
angles  to  but  often  nearly  or  quite 
parallel  to  the  guard  cells,  and  of 
which  one  is  usuallj^  considerably 
larger  than  the  other;  hairs  abun- 
dant on  both  faces,  iDarallel  to  the 
veins,  appressed,  lying  in  slight 
grooves  of  the  epidermis,  each  attached  b}^  its  middle  (hence  2-armed) 
to  a  short  cylindrical  foot  cell,  which  is  bordered  by  several  wedge- 
shaped  (as  seen  from  above)  radiallj^  arranged  epidermis  cells,  the 
free  cell  with  a  very  thick,  warty  cuticle. 

Hypodermal  collenchynla  (not  very  typical),  in  1  or  2  layers  above 
and  3  or  4  below  the  principal  veins,  intermitting  the  chlorenchyma 
in  full-grown  leaves. 

Chlorencliyma:  Palisade  2-layered,  the  cells  rather  short;  pneu- 
matic tissue  rather  compact,  not  well  differentiated  from  the  palisade, 
but  its  cells  more  nearly  isodiametric  and  containing  less  chlorophyll. 
Mestome  hundles  (of  larger  veins),  with  some  stereome  below  the 
leptome  and  a  small  group  of  collenchj^ma  above  the  hadrome,  which 
finall}^  becomes  continuous  with  the  subepidermal  group  of  col- 
lenchj^ma. 


Fig.  47.—Li2ypia  nodiflora— stomata  and  hairs, 
a,  Stomata  on  leaf;  t»,  hair  and  stoma  on  ventral 
leaf  surface;  c,  hair  on  dorsal  surface.  Scale 
240. 


'  Compare  Warming.  Halofyt-Studier,  p.  3oo,  and  Solereder,  Syst.  Anat.,p.  713, 


ANATOMY    OF    MONNIERA    AND    SOLIDAGO.  305 

MONNIERA   MONNIERA    (L.)    BRITTOX.' 

Occurs  in  2  forms;  one  in  shallow  pools,  largely  submersed,  willi 
long  stems,  elongatcnl  internodes,  and  larger  loaves;  the  other  terres- 
trial, in  wet  sand,  with  short,  creeping  stems,  contracted  internodes 
and  smaller  leaves. 

(a)  Aquatic  form.  Structure  that  of  a  partially  submersed  hydro- 
phyte, with  thin- walled  tissues,  much  reduced  mestome  system,  no 
mechanical  tissue,  etc. 

Leaf  isolateral. 

Epidermis:  Cells  with  undulate  lateral  walls,  the  walls  thin  except 
the  outer,  which  is  somewhat  thickened;  cuticle  delicately  wrinkled; 
stomata  more  numerous  on  the  dorsal  surface,  guard  cells  about  level 
with  the  epidermis,  bordered  by  2  to  4  ordinary  epidermal  cells;  hairs 
none. 

Chlorenchynia  homogeneous,  palisade  none. 

Mestome  bundles  immediately  bordered  by  chlorenchyma,  not  rein- 
forced by  stereome  or  collenchyma. 

Stem:  Epidermis  as  in  the  leaf. 

Cortical  parenchyma  in  1  or  2  continuous  layers  just  beneath  the 
epidermis  and. around  the  central  cylinder,  elsewhere  in  1-layered 
plates,  separating  the  large  lacunes. 

Mestome  cylinder  composed  of  several  bundles,  inclosing  a  small 
quantity  of  pith. 

(6)  Terrestrial  form.  The  only  tangible  differences  from  the  aquatic 
form  are:  Stomata  about  equally  numerous  on  both  leaf  surfaces; 
mestome  bundles  somewhat  more  developed  and  walls  of  the  vessels 
more  lignified;  mesophyll  somewhat  more  compact. 

Solid  AGO  sempervirens  L.^ 

Leaf  somewhat  fleshy,  vertical  or  nearly  so,  apjjroximately  isolat- 
eral. 

Epidermis:  Cells  with  nonundulate  radial  walls,  only  the  outer 
strongly  thickened,  except  above  and  below  the  larger  veins;  cuticle 
strongly  wrinkled;  stomata  numerous  on  both  faces  with  guard  cells 
level  with  the  surface,  bordered  by  usually  4  ordinary  epidermal  cells; 
hairs  none. 

Hypodermal  collenchyma  in  only  1  or  2  narrow  layers  above  and 
3  or  4  wide  layers  below  the  larger  veins. 

CJdorenchyma  homogeneous,  none  of  it  typical  palisade,  frequently 
interrupted,  especially  opposite  the  mestome  bundles,  b}'  plates  of 
colorless,  thin- walled  parenchyma  (water  tissue),  which  extend  froni 
the  ventral  to  the  dorsal  epidermis,  and  ultimately  break  down  into 
large  lacunes  close  beneath  the  epidermis. 

^  Herpestis  mouuiera  H.  B.  K. 
Th( 

2965- 


306  THE    PLANT    COVERING    OF    OCRACOKE    ISLAND. 

Ducts  (probablj^  resiniferous)  numerous,  especially  near  the  dorsal 
surface,  a^iparently  always  Ij^ing  in  the  lilates  of  Avater  tissue,  one 
below  the  leptome  of  the  mid  vein. 

Mestome  bundles  of  the  larger  veins  with  a  narrow  (in  transA'erse 
section  crescent-shaped)  group  of  comparatively  thin- walled  stereome 
above  the  hadrome.^ 

Aster  tenuifolius  L. 

Leaves  narrow,  almost  vertical,  isolateral,  thick,  with  a  deep  groove 
on  the  dorsal  surface  on  each  side  of  the  midvein,  margins  slightly 
incurved. 

Epidermis:  Cells  comi)aratively  large,  walls  not  undulate,  the  outer 
greatly  thickened;  cuticle  wrinkled  and  with  slight  furrows  corre- 
sponding to  the  radial  walls  of  the  epidermal  cells ;  stomata  rather 
few  and  large,  the  guard  cells  slightly  sunken,  mostly  somewhat 
deflected  in  direction  from  that  of  the  leaf  axis,  bordered  by  usually 
3  ordinary  epidermis  cells;  hairs  none. 

♦  Hypodermal  collenchyma  in  a  few  narrow  layers  above  and  rather 
wide  layers  below  the  midvein. 

CMorenchyma  consisting  of  palisade  with  high,  narrow  cells,  in 
about  2  layers  on  both  faces,  strongly  converging  toward  the  mid- 
vein,  especially  on  the  ventral  side. 

Colorless  parenchyma  (water- storage  tissue)  occupying  the  interior 
of  the  leaf  in  small  quantity,  and  surrounding  the  midvein,  where  it 
replaces  the  palisade. 

Mestome  bundles  not  reinforced  by  stereome. 

Aster  subulatus  Michx. 

Leaves  wider  and  thinner  than  in  the  preceding,  almost  vertical, 
isolateral,  flat,  impressed  above  the  midvein,  which  below  is  i^romi- 
nent,  with  a  furroA^^  on  each  side  of  it. 

Epidermis:  Cell  Avails  not  undulate,  thick,  the  outer  A^er}^  thick, 
the  inner  collenchymatic-thickened  A\^here  hypodermal  collenchyma 
occurs;  cuticle  wrinkled;  stomata,  with  guard  cells  lying  parallel  to 
the  leaf  axis,  level  Avith  the  surface;  hairs  none. 

Hypodermal  collencliyma  above  and  below  the  A^eins  (about  4  laj^ers 
betAveen  the  leptome  of  the  midA^ein  and  the  dorsal  epidermis)  and  in 
the  marginal  angles. 

CMorenchyma,  of  compact  palisade,  occupying  i^ractically  the  entire 
thickness  of  the  leaf  except  Avhere  collenchyma  occurs  and  about  the 
midA^ein. 

'The  leaves  of  nonmaritime  species  of  Solidago  (e.  g.,  S.  petiolaris,  S.  neglecta, 
and  S.  erecta)  exhibit  some  interesting  differences  from  S.  sempervirens.  All  three 
have  bifacial  leaves  with  compact  palisade  and  open  pneumatic  tissue  (chloren- 
chyma  least  differentiated  in  S.  petiolaris).  Stomata  few  {S.  erecta,  S.  neglecta) 
or  none  {S.  petiolaris)  on  the  ventral  surface,  guard  cells  slightly  prominent  on 
the  dorsal  surface.  Hairs  along  the  veins,  especially  on  the  dorsal  face  in  S.  petio- 
laris, 3  or  4  celled   sharp-pointed,  bent. 


ANATOMY    OF    BACCHARIS    HALIMIFOLIA.  307 

Colorless  parejicliynia  (water-stonige  tissue)  above  and  on  each  side 
of  the  mid  vein. 

Mestome  bundles  without  stereome  supports,  but  with  a  small  irreg- 
ular group  of  collenehynia  lying  outside  the  hadrome.^ 

BaCCHARIS    HALIMIFOLIA    L, 

Leaves  thickish,  nearly  vertical,  isolateral. 

Epidermis:  Cell  walls  not  undulate,  thickened,  the  outer  ones  greatly 
so;  cuticle  warty,  especiall}^  on  the  dorsal  surface;  stomata  mostly 
parallel  to  the  veins,  but  many  somewhat  deflected,  guard  cells  slightly 
prominent,  each  stoma  radially  bordered  by  4  or  o  small  epidermis 
cells. 

Colleyicliyma  (hypodermal)  replacing  chlorenchyma  above  and  below 
the  larger  veins  (0  or  7  layers  below  the  leptome  of  the  midvein), 
containing  no  ducts. ^ 

Chlorenchyma:  Palisade  occupying  the  whole  thickness  of  the  leaf 
between  the  veins,  rather  open,  especiall}^  that  in  the  interior  of  the  leaf 
(but  typical  pneumatic  tissue  none),  converging  toward  the  midvein 
on  the  dorsal  side;  large,  deep  air  chambers  underneath  the  stomata. 

Colorless  parenchyma  (water  tissue)  in  2  layers  on  each  side  of  the 
midvein  (cells  circular  in  cross  section),  in  a  single  layer  entirely  sur- 
rounding the  smaller  bundles. 

'  Three  nonmaritime  species  of  Aster  were  selected  for  comparison  with  the  two 
salt-marsh  species:  A.  puniceuH,  a  broad-leaved  plant  of  boggy  ground,  and  .1. 
dumosus  and  A.  ericoides,  narrow-leaved  species  of  dry,  sandy  soil. 

A.  ericoides  has  a  practically  isolateral  leaf,  epidermis  alike  on  both  faces,  with 
undulate  radial  and  thickened  outer  walls,  finely  wrinkled  cuticle,  guard  cells  of 
the  stomata  level  with  the  ventral  surface,  slightly  prominent  on  the  dorsal  sur- 
face; chlorenchyma  near  both  surfaces  compact  and  small-celled,  more  open  and 
larger-celled  in  the  interior  of  the  leaf;  hypodermal  collenchyma  in  '2  layers  above 
and  below  the  midvein;  water  parenchyma  none. 

^4.  dumosus  has  a  distinctly  bifacial  leaf,  epidermis  much  as  in  .1.  ericoides,  but 
the  2  surfaces  more  differentiated,  the  ventral  with  radial  cell  walls  less  undulate 
and  outer  walls  less  thickened  than  in  ^4.  ericoides,  cells  larger  and  stomata  much 
fewer  on  the  ventral  surface,  the  dorsal  with  radial  walls  more  strongly  undu- 
late, and  scattered,  slender,  pointed,  few-celled  hairs  along  the  veins:  ])alisade  com- 
pact, pneumatic  tissue  open:  veins  supported  by  hypodermal  collenchymatic  tissue. 

A.  puniceus  shows,  of  course,  the  greatest  amount  of  difference  from  the  salt- 
marsh  forms.  It  has  a  flat,  approximately  horizontal,  bifacial  leaf.  The  ventral 
surface  is  rough  with  thick- walled,  prickle-like,  1-celled  hairs,  mixed  ^vith  scat- 
tered, longer,  more  slender,  and  thinner-walled  hairs:  the  stomata  lie  in  all  direc- 
tions in  and  have  their  guard  cells  level  with  the  dorsal  surface,  but  are  wanting 
on  the  ventral  face:  the  cuticle  is  smooth;  the  chlorenchyma  is  differentiate<l  into 
a  single  layer  of  compact  palisade  and  a  few  layers  of  rather  open  pneumatic  tis- 
sue; no  colorless  parenchyma  occurs  inside  the  epidermis. 

On  the  whole  the  salt-marsh  Asters  show  less  anatomical  divergence  from  inland 
forms  than  does  the  salt-marsh  Solidago.  Of  the  two  species,  .1.  fenidfoliKs 
exhibits  a  more  distinctive  halophytic,  or  rather  xerophytic,  structure  than  does 
^4.  suhulatiis. 

-Warming,  Halofyt-Studier,  p.  195,  describes  ducts  which  occur  in  the  collen- 
chyma of  the  leaf  of  Baccharis  dioica. 


308 


THE    PLANT    COVERING    OF    OCRACOKE    ISLAND. 


Mestoine  bundles  Avith  a  strong  groui)  of  stereome  on\y  outside  ihe 
hadrome  in  young  leaves,  in  older  leaves  a  corresponding  grouj)  of 
more  numerous  and  smaller  cells  outside  the  leptome  also. 

IVA   FRUTESCENS   L.^ 

Leaf  thick,  usuall}^  almost  vertical,  nearly  isolateral. 
Epidermis  cells  small,   walls  not   undulate,   thick,    especially  the 

outer;  cuticle  wrinkled,  especially  above 
and  below  the  veins;  stomata  small,  about 
equally  numerous  on  both  surfaces,  the 
guard  cells  sunken,  especially  on  the  dor- 
sal surface,  lying  irregularly  in  all  direc- 
tions; hairs  on  both  surfaces  (fig.  48)  ap- 
pressed,  antrorse,  thick-walled,  2  or  3 
celled,  sharp-pointed,  the  terminal  cell 
abruptly  narrowed  just  above  its  base, 
each  hair  borne  upon  5  or  6  radially 
arranged  foot  cells  which  form  a  cushion 
that  projects  above  the  level  of  the  epider- 
mis; glands,  2  or  3  celled,  sessile,  nearly 
spherical,  almost  filling  depressions  in  the 
epidermis  and  rising  slightly  above  its  gen- 
eral level. 

Hypoderriial    collenchyma    in    strong 
groups  above  and  below  the  larger  veins 
(about  10  layers  above  and  below  the  mid  vein). 

Chlorenchyma  palisadic,  in  several  layers,  the  cells  small  and 
narrow,  those  near  the  mid  vein  converging  toward  it;  palisade  fre- 
quently interrupted  (especiall}^  opposite  the  mestome  bundles)  by  a 
few  rows  of  thin- walled,  colorless  parenchyma  (water  tissue),  which 
ultimately  breaks  down  into  lacunes.  Large  ducts,  each  surrounded 
by  a  sheath  of  small  cells,  occur  in  the  water  tissue,  esijeciall}^  on  the 
ventral  side  of  the  leaf. 

Mestome  bundles  with  a  little  thin-walled  stereome  over  the 
hadrome.^ 


Fig,  48.— Ira  frutescens— hair  from 
ventral  leaf  surface.    Scale  320. 


^  The  material  examined  was  collected  near  Virginia  Beach,  Virginia. 

-  Iva  imbrlcata  Walt,  is  a  common  plant  of  the  Atlantic  sand  strand  in  the 
Southeastern  States,  although  not  observed  upon  Ocracoke  Island.  It  presents 
some  interesting  differences  from  the  salt-marsh  /.  frufescens.  The  leaves  exam- 
ined were  collected  near  Cape  Henry,  Virginia. 

The  plant  is  strongly  arom  itlc,  the  leaf  perfectly  isolateral,  fleshy  and  smooth. 

Epidennis:  cells  much  larger:  cuticle  not  wrinkled;  s  omata  with  guard  cells 
level  with  the  ventral  surface,  somewhat  sunken  on  the  dorsal;  hairs  none. 

Collenchuma  less  strongly  developed  than  in  /.  frutescens. 

Chlorenchyma  consisting  of  2  or  3  layers  of  palisade  on  both  surfaces. 

Colorless  parenchyma  (water-storage  tissue),  filling  the  interior  of  the  leaf  and 
interrupting  the  palisade  above  and  below  all  the  veins. 

Mestoine  bundles  lying  in  the  midst  of  the  water-storage  tissue;  stereome  none. 

The  most  important  differences  in  /.  inibricata  are  the  strong  development  of 


ANATOMY    OF    BORRICHIA    FRUTESCENS. 


309 


BORRICHIA   FRUTESCENS    (L.)    DC'. 

Leaves  (fig.  49)  fleshy,  jilniost  vertical,  imperfectly  isolateral,  the  sur- 
face glistening,  whitish,  mealy  looking,  especially  in  young  leaves. 

Epidermis  (fig.  49)  with  small,  thin- walled  cells,  very  many  of 
which  are  extended  by  tangential  division  into  commonly  2  to  4 
celled,  thin- walled,  pointed,  usually  bent  haii's  (fig.  50),'  the  whole 
forming  a  very  dense  covering  and  giving  the  leaf  its  peculiar,  glis- 
tening aspect;  stomata  only  on  the  ventral  surface,  the  guard  cells 
slightly  sunken. 

Collenchyma  (hypodermal)  in  several  layers  abov(^  and  l)elow  the 
large  mestome  bundles  (five  in  the  midvein). 

CJdorenchyma  consisting  of  very  compact  palisade,  2-layered  on 
.both  surfaces;  pneumatic  tissue  none. 

Colorless  parenchyma  (water-storage  tissue)  (fig.  49)  occupying  the 


FiqA9 .—Borrichia  frutescens—\ea,{  section.  Trans- 
verse section,  showing  epidermis  of  ventral  sur- 
face (Ep);  palisade  (P);  colorless  parenchyma 
(C  T);  hadrome  (H)  and  leptome  (L)  of  a  small 
mestome  bundle;  and  epidermis  of  dorsal  surface 
(ep).    Scale  320. 


Pig.  50.— Borrichia 
frutescens—leat- 
hairs.    Scale  340. 


interior  of  the  leaf  and  forming  rather  more  than  one-half  its  thick- 
ness, at  somewhat  regular  intervals  displacing  the  i>alisade  on  tlie 
dorsal  side  and  extending  to  the  epidermis.  Ducts  (on  the  ventral 
side)  frequent  just  beneath  these  extensions. 

Mestome  bundles  of  the  veins  (fig.  49)  lying  deep  in  the  water-storage 
tissue;  reinforced  on  the  leptome  side  b}'  a  strong  group  of  very  thick- 
walled  stereome,  on  the  hadroine  side  by  a  smaller  group;  leptome 
and  its  elements  beautifully  differentiated,  the  sieve  tubes  each  witli 

water-storage  tissue  in  the  interior  of  the  leaf  and  the  absence  of  hairs— just  the 
converse  of  what  one  would  expect  as  the  differential  characters  between  a  dune 
and  a  salt-marsh  species. 

'  The  apical  cells  are  easily  broken  off,  so  that  in  older  leaves  the  covering  appears 
to  consist  of  rounded,  usually  biceliular  papillae. 


310 


THE    PLANT    COVERING    OF    OCRACOKE    ISLAND. 


a  companion  cell  and   a   band  of   four  or  five  cribrile  parenchyma 

cells.  1 

Leaf  anatomy  of  salt-marsh  species. 


[The  sign  x  indicates  presence  of  character;  ± 

Its  imperf 

ect  development.] 

Leaf. 

Epidermis. 

Cuticle. 

Ul 

Species. 

i 

t 

2 
1 

-2 

Relatively 
thick. 

Thick. 

1 

■S 

H 

it 

X 

X        ■           X 

X 

X 

X 

X               X 

X 

Titjcifl  marina 

X 

X 

Kosteletzkya  virginica 

X 

± 

Vincetoxicum  palustre 

X 
X 

X 
X 
X 
X 
X 
X 
X 

Lippia  nodiflora 

± 

X 

I 

X 
X 
X 

± 

Iva  frutescens 



X 
X 
X 

X 
X 
X 
X 
X 

Aster  tenuifollus 

Baccharis  halimifolia 

X 
X 

X 

Characters  given  under  species  of  the  "sand  strand,"  page 


1  Borrichia  arhorescens  (compare  Warming,  Halofyt-Studier,  p.  212)  is  a  very- 
similar  but  larger  plant  of  the  tropical  American  strand.  It  differs  from  B.  frutes- 
cens in  the  following  particulars,  the  characters  being  taken  from  material  col- 
lected in  South  Florida  and  Porto  Rico: 

Hairs  much  thicker-walled,  entirely  disappearing  in  old  (more  than  1  year 
old?)  leaves;  stomata  on  both  surfaces,  with  guard  cells  slightly  prominent  on  the 
ventral  face,  less  numerous  and  with  guard  cells  slightly  sunken  on  the  dorsal 
face;  epidermal  cell  walls,  especially  the  outer,  thick;  palisade  interrupted  both 
above  and  below  by  extensions  of  the  water-storage  tissue,  which  on  the  ventral 
side  ultimately  disorganize  and  form  large  lacunes;  hypodermal  coUenchyma 
occurring  where  the  palisade  is  interrupted  on  the  ventral  side;  coUenchyma 
taking  the  place  of  stereome  as  supports  of  the  veins,  especially  strong  on  the  lep- 
tome  side. 

From  Warming's  description  and  figure  of  B.  arhorescens  my  specimens  showed 
important  differences:  (1)  The  presence  of  hairs  (elsewhere  in  the  same  paper 
Warming  mentions  their  occurrence  in  this  species) ;  (2)  stomata  with  guard  cells 
slightly  prominent  on  the  ventral  surface  (Warming  writes  "stomata  sunken""); 
(3)  coUenchyma  present  and  strongly  developed;  (4)  mestome  bundles  in  three 
planes  (one  according  to  Warming) ,  some  small  ones  being  situated  near  the  upper 
and  the  lower  epidermis,  while  the  midvein  is  central  in  the  water-storage  tissue. 


ANATOMICAL    SUMMARY    OF    SALT-MAKSH    SPECIES. 


311 


Leaf  anatomy  of  salt-inarsh  .s^«'c/V.s — (  ontiuned. 
[The  sign  x  indicates  presence  of  character;  ±  its  imperfect  development.] 


. 

Epidermis. 

Stomata. 

Species. 

1 

1  • 

•if 

1 

1 . 
^1 

cc 
^    . 

1 

i 

0 

1 

0    . 

■>-'  Cfi 

i 

•a 

! 

u 

1 

Triglochin  striata 

X 

X 

X 

X 

Spartina  stricta ' 

J  uncus  roemerianus  . 

X 

X 

X 

i 

X 

Tissa  marina 

X 
X 
X 

X 

Kosteletzkya  virginica 

X 
X 
X 
X 
X 
X 
X 
X 
X 
X 



Ammania  Ivoehuei 

± 

Vincetoxicum  palustre  . . . 

X 

Lipi)ia  nodiflora -.. 

± 



X 

Monniera  monniera 

X 

Iva  f  rutescens -  - 

X 

X 

Solidago  sempervirens 

X 

Aster  tenuif olius 

X 

X 

i 

Aster  subulatus. 

X 

Baccharis  halimifolia 

X 

Borrichia  f rutescens 

X 

Epidermis. 

Hypoder- 
mal  collen 
chyma  or 
collenchy- 
matic  tissue. 

Hairs. 

Species. 

eg 

U 

Is 

f 

1 
1 

1 

IS 

1 

cc 

c 

1 

i 

"O  U 

0  o 

3 

1 

la 

a 
O 

2 

Triglochin  striata 

Spartina  stricta  ' 

Juncus  roemerianus  . . 

Sesuvium  maritimum. . 

1 

Tissa  marina 

X 
X 

X 

X 

Kosteletzkya  virginica 

>^' 

X 

X 

Ammania  koehnei- . 

Vincetoxicum  palustre 

Lippia  nodiflora 

X 

X 

X 

X 

Monniera  monniera 

Iva  f rutescens... 

X 

X 

X 

X 

X 
X 
X 

Solidago  sempervirens 

Aster  tenuifolius 

Aster  subulatus 

Baccharis  halimifolia  .. 

X 

Borrichia  frutescens. . . 

X 

X 

X 

X 

■ 

1 

^ 1 

1  Characters  given  under  sjiecies  of  tlio  "sand  strand."  page 


312 


THE    PLANT    COVERING    OF    OCKACOKE    ISLAND. 


Leaf  anatomy  of  salt-marsh  spec/'e.s— Continued,  ♦ 

[The  si^a  x  indicates  presence  of  character;  ±  its  imperfect  development.] 


Stereome. 

Water 
Chlorenchyma.                   paren- 
chyma. 

Mestome 
bundles. 

Species. 

1 

1 

05 

1  . 

t 

I 

o 
W 

t 

(D 

4i 

H 

ll 
II 

be 

.S 

II 
1 

it 

5 . 

a® 

1 

2 

03 

ft"' 

X 

X      1     X 

Sioartina  stricta^ 

Juncus  roemerianais... 

X 

X 

X 
X 

X 

X 
X 

X 
X 
X 
X 
X 
X 
X 



X 

X 

X 

Kosteletzkya  virginica. 

X 

X 

X 

Vincetoxicum  palustre 

X 

± 

X 

X 
X 

X 
X 

X 

X 
X 

Solidago  sempervirens. 

X 
X 

X 

X 

X 
X 

X 

X 

X 

X 

X 

X 

1 

1  Characters  given  under  species  of  the  "sand  strand,"  p.  389. 

GEOGRAPHICAL  AFFINITIES  OF  THE  FLORA. 

According  to  its  geographic  position,  Ocracoke  Island  lies  well 
within  the  Anstro riparian  area  of  the  Lower  Austral  life  zone  in  North 
America.^  For  two  reasons,  however,  this  relationship  of  its  flora  is 
somewhat  obscured:  (1)  By  the  large  proportion  of  strand  species, 
many  of  which  have  a  very  extensive  geographic  range;  and  (2)  by  the 
absence  of  many  of  the  most  characteristic  species  of  the  Austro- 
riparian  area,  due  to  the  peculiar  physical  environment. 

Of  the  total  number  of  species  of  embryophytes  (about  135)  collected 
or  observed  upon  Ocracoke  Island,  between  one-fourth  and  one-third 
may  be  designated  as  maritime,  i.  e.,  normally  occurring  only  in  the 
salt  marshes  or  on  the  sand  strand  bordering  the  ocean.  These  may 
be  segregated  into  4  groups,  according  to  geographical  range : 

1.  Species  occurring  also  on  the  coasts  of  tropical  America. 

A  prefixed  asterisk  (*)  indicates  that  the  species  does  not  extend 
north  of  the  mouth  of  Chesapeake  Bay;  a  prefixed  dagger  (f)  that 
the  northern  limit  is  in  North  Carolina,  probably  not  far  from  Ocra- 
coke. Triglochin  striata  and  Monniera  monniera  extend  north  to 
eastern  Maryland. 

'Merriam,  Geogr.  Distrib.  p.  211:  Life  Zones  p.  45,  map. 


GEOGRAPHICAL    AFFINITIES    OF    THE    FLORA.  313 

Triglochin  striata  R.  &  P.  \  Yucca  aloifolia  L. 

*Qaercus  vir-ginianaLi.^  * Physalis  viacosa  ^L. 
\Chloris  petraea  Sw.  Monniera  monniera  H,  B.  K. 

* Uniola xKinicuUda  L.  *Borrichia  frutescena  L. 

^Fimbristylis  spadicea  Vahl.  \Ipomoea  sagittata  Cav. 

2.  Species  mostly  or  entirely  confined  to  the  seacoast  of  the  Austro- 
riparian  area:  Zdidhoxyluni  dava-lievculis  and,  X)ossibly,  Ilex  roini- 
toria  extend  northward  to  Virginia,  while  the  rest  attain  their  northern 
limit  in  North  Carolina. 

Miihlenbergia  filipes  M.  A.  Curtis.  Ilex  vomitoria  Ait. 

Yucca  gloriosa  L.  Opuntia  pes-corvi  Le  Conte. 

Croton  maritimus  Walt.  Vincetoxicum palustre  (Pursh)  A.  Gray. 

Zanthoocylum  clava-herculis  L. 

3.  Species  confined  to  the  Atlantic  seacoast  of  North  America  and 
ranging  north  of  the  Austroriparian  area.  The  northern  limit  of 
each  is  cited  as  given  in  Britton  &  Brown's  Illustrated  Flora. 

Panicum    amarum    minus    Vasey   &  Oenothera   humifusa  Nutt.    (New  Jer- 
Scribn.  (Connecticut).  sey). 

Spartina    patens  (Ait.)   Muhl.    (Nova  Limonium  earolinianum  (Muhl.)  Brit- 
Scotia),  ton  (Labrador). 

Distichlis  spicata  (L. )  Greene  -  (Maine) .  Iva  frutescens  L.  (Massachusetts) . 

Juncus  roemerianus  Scheele  (New  Jer-  Solidago  sempervirens  L.  (New  Bruns- 
sey).  wick). 

Sesuvium  maritimum   (Walt.)  B.  S.  P.  Aster  tenuifolius  h.  (Massachusetts). 

(New  York).  Aster  siibidat us   Michx.   (New   Hamp- 

Euphorbia    polygonifolia     L.    (Rhode         shire). 

Island).  Baccharis    halimifolia    L.    (Massachu- 

Kosteletzkya  virginica  L.  (New  York).         setts). 

Ammania fcoe/mei Britton  (New  Jersey). 

4.  Species  occurring  also  on  the  seacoast  of  the  northern  hemisphere 
in  the  Old  World. 

Spartina  stricta  (Ait. )  Roth.  Salsola  kali  L. 

Atriplex  hastata  Ij.  Tissa  marina  {Ij.)  Britton. 

Salicornia  herbacea  L. 

Of  the  nonmaritime  species  of  the  island,  fifteen  are  introduced 
and  are  chiefiy  weeds  of  American  origin.  The  remainder  (about 
two-thirds  of  the  total  flora)  includes  several  mainly  tropical  species, 
such  as Lippia  nodiflora  Michx.,  Centella  asiatica (L.)  Urban,  Parietn- 
ria  deb  His  For  St.,  and  Tillandsla  tts?ieoidesL.,  which,  while  hardly  mari- 
time, are  found  usually  near  the  seacoast  in  the  Austrorix)arian  area. 
Finally,  after  excluding  all  the  preceding  categories  except  the  second 
of  strand  plants,  we  have  a  list  of  species  among  which  the  Austro- 
riparian element  is  sufficiently  predominant  to  leave  no  question  as 
to  the  general  affinity  of  the  flora. 

As  previously  remarked,  however,  many  of  the  plants  most  cliar- 

'  Normally  a  strand  plant  in  Virgfinia  and  North  Carolina. 
-The  typical  form. 


314  THE    PLANT    COVERING    OF    OCKACOKE    ISLAND. 

acteristic  of  the  whole  Austroriparian  area,  and  abundant  on  the 
mainland,  scarcely  30  kilometers  distant,  are  wanting  upon  Ocracoke 
Island.  Notable  among  these  absentees  are  the  pines  {Pin  uspalustris^ 
P.  taeda),  the  gums  (Xyssa  spp.),  the  bald  cypress  {Taxodiuin  dis- 
tichum),  the  deciduous  oaks,  the  cane  (Arundinaria  macrosperma), 
species  of  Erianthus,  Carex  verrucosa,  Smilax  laurifolla,  and  Bei^- 
chemia  scandens.  Hardly  less  striking  is  the  nonoccurrence  of  most  of 
the  bright- flowered  herbs  that  abound  in  the  pine  forests  on  the  west 
shore  of  Pamlico  Sound.  Such  are  species  of  Coreopsis,  Helianthus, 
Lacinaria  (Liatris),  Eupatorium,  Solidago,  Rhexia,  Gerardia,  H3^i3er- 
icum,  Sarracenia,  Habenaria,  and  Polygala.  The  unfavorable  environ- 
ment is  doubtless  responsible  for  the  absence  of  many  of  these  plants, 
conditions  ui)on  the  island  being  suitable  only  to  tlie  hardiest  species. 
Scarcity  of  shade,  of  humus,  and  of  fresh  water  accounts  in  like  man- 
ner for  the  poverty  of  the  flora  in  most  of  the  lower  forms,  such  as 
fresh-water  algae,  fungi,  hepaticae,  mosses,  and  ferns.  The  numerous 
arrangements  b}^  which  many  of  the  higher  plants  are  protected  against 
excessive  loss  of  water  maj^  also  serve  in  some  measure  for  protection 
against  parasitic  leaf  fungi,  and  may  partly  account  for  the  com- 
parative scarcity  of  the  latter. 

The  general  aspect  of  the  j)lant  covering  is  not  attractive.  Bright 
green  foliage  and  flowers  of  brilliant  coloring  are  too  scarce  to  make 
much  impression,  while,  except  in  the  salt  marshes,  the  plants  are 
usually  so  scattered  that  it  is  the  soil  which  gives  tone  to  the  land- 
scape. Furthermore,  the  trees  and  shrubs  are  mostly  characterized 
by  gnarled  trunks,  many  dead  branches,  and  ragged  foliage,  as  a 
result  of  exposure  to  sand-laden  winds.  Altogether,  the  picture  is 
one  of  somber  monotony. 

LIST  OF  PLANTS  COLLECTED  AND  OBSERVED. 

[The  prefixed  asterisk  denotes  that  the  plant  is  introduced.] 

LICHENES. 

Usnea  barbata  L. 

Ramalina  tnontagnei  De  Not. 

MUSCI. 

Bryum  argenteum  L. 
Rhynchostegium  serrulatum  Hedw. 

POLYPODIACEAE. 

Aspleniuin platyneuron  (L.)  Oakes.     {A.  ebeneumA.it.) 

PINACEAE. 

Juniper  us  virginiana  L. 

TYPHACEAE. 
Typha  latifolia  L. 

SCHEUCHZERIACEAE, 

Triglochin  striata  Ruiz  &  Pav. 


LIST    OF    SPECIES.  315 

POACEAE. 

Aridrojjogou  glomeratus  (Walt.)  B.  S.  P.     (A.  laacronriis  Michx. ; 

Paspalum  ciliatifoUmn  Michx. 

PaHpalam  distichum  L. 

Paspalum  laeve  JNlichx. 

Syntlierisviafiinbriata  (Smith)  Nash.     (Digitaria  Jivihr'tafa  Smith.) 

PauicKiii  ainarum  minus  Vasey  &  Scribner. 

Pauicuiii  lattuginosum  Ell.  (?) 

Panicuiu  laxijlorum  Lam. 

Panicum  neuranthum  Griseb. 

Panic um  walteri  Pursh. 

OjjI  is  menus  setarius  (Lam.)  Roem.  &  Schult. 

Chaetochloa   imherbis  pereiinis  (Hall)  Scribn.    &   Merrill.     (C.  versicolor 
Bicknell.) 

Homalocenchrus  virginicus  (Willd.)  Britton.     ( Leers ia  virginica  Willd.) 

MuhlenhcrgiafilijjesM.  A.  Curtis. 
"^Sporobolus  indicus  (L.)  R.  Br. 
*Capriola  dactylon  (L.)  Kuntze.     {Cynodon  dacftjlonPeia.) 

Spartina patens  {Ait.)  Muhl.     {S.  jancea'EAl.) 

Spartina  stricta  (Ait.)  Roth. 

Chloris  p>etraea  Sw. 
*Eleusine  indica  (L.)  Gaertn. 

Triplasis purpurea  (Walt.)  Chapm. 

Eragrostis  nitida  (Ell.)  Chapm. 

Uniola  laxa  (L.)  B.  S.  P.     {U.  gracilis  Michx.) 

Uniola  paniculata  L. 

Distichlis  spicata  (L.)  Greene.     (D.  maritima  Raf.) 

CYPERACEAE. 

Cyperus  cylindricus  (Ell.)  Britton.     (C.  torreyi  Britton.) 

Cyperus  echinatus  (Ell.)  Wood.     (C  haldwinii  Torr.) 

Cyperus  nuttallii  Eddy. 

Cyperus  speciosus  Vahl. 

Eleocliaris  sp. 

Dickromena  colorata  (L.)  A.  S.  Hitchcock.     (7).  leucocephala  Michx.) 

Fimbristylis  spadicea  (L.)  Vahl. 

Scir2)us  americanus  Pers.     {S.  pungens  Vahl.) 

Scltria  verticillata  Muhl. 

Cladium  effusiwi  Torr. 

ARACEAE. 

Acorus  calamus  L. 

Tillandsia  usyieoides  L. 


BROMELIACEAE. 
JUNCACEAE. 


Juncus  dichotomus  Ell. 
Juncus  roeinerianus  Scheele. 
Juncus  scirpoides  Lam. 

LILIACEAE. 
Yucca  aloi folia  L. 
Yucca  gloriosa  L. 

SMILACEAE. 

Smilax  bona-no,v  h.     (S.  tamnoidoi  A.  Gray.) 


31(J  THE    PLANT    COVERING    OF    OCRACOKE    ISLAND. 

MYRICACEAE. 

Myrica  ca^'olinensis  Mill. 
Myrica  cerifera  L. 

FAGACEAE. 

Quercus  virginiana  L.     {Q.  virens  Ait.) 

MORACEAE. 

*  Ficus  carica  L. 

*  Brousso7ietia  pajyyrifera  (L.)  Vent. 

URTICACEAE. 

Parietaria  debilis  Forst. 

POLYGONACEAE. 

Polygonum  punctatum  Ell. 
Rumex  sp. 

CHENOPODIACEAE. 

*  Chenopodium  anthelminticum  L. 
Atriplex  hastata  L. 
Salicornia  herbacea  L. 
Salsola  kali  L. 

PHYTOLACCACEAE. 

Phytolacca  decandra  L. 

AIZOACEAE. 

Sesuvium  maritimiim  (Walt.)  B.  S.  P.     {S.  pentandrum  Ell.) 
Mollugo  verticillata  L. 

ALSINACEAE. 

Tissa  marina  (L.)  Britton.     (Spergularia  salina  J.  &  C.  Presl.) 

ROSACEAE. 

Ruhus  trivialis  Michx. 

CAESALPINACEAE. 

*  Cassia  occidentalis  L. 

VICIACEAE. 

Aeschynomene  virginica  (L.)  B.  S.  P.     {A.  Iiispida  Willd.) 
Meihomia paniculata  (L.)  Kuntze.     (Desmodium paniculatum  DC) 
Oalactia  volubilis  (L.)  Britton.     {G.  pilosa  Ell.) 

LINACEAE. 

Linum  medium  (Planch. )  Britton. 

RUTACEAE. 

Zanthoxylum  clava-hercidis  L. 

EUPHORBIACEAE. 

Croton  maritimus  Walt. 
Acalypha  gracilens  A.  Gray. 
Euphorbia  polygonifolia  L. 

ANACARDIACEAE. 

Rhus  radicans  L. 


LIST    OF    SPECIES.  317 

ILICACEAE. 

Ilex  glabra  (L. )  A.  Gray. 

Ilex  opaca  Ait. 

Ilex  vomitoria  Ait.     (/.  cassine  Walt.) 

VITACEAE. 

Vitis  aestivalis  Michx. 

MALVACEAE. 

Kosteletzky a  virgin! ca  (L. )  A.  GJ-ray. 
Hibiscus  moscheutos  L. 
*  Gossypium  herhaceurn  L. 

HYPERICACEAE. 

Ascyrum  hypericoides  L. 

CISTACEAE. 
Lechea  villosa  EW.     {L.  major  Michx.) 

CACTACEAE. 
Opuntia  pes-corvi  Le  Conte. 

LYTHRACEAE. 
Ammania  koehnei  Britt. 

ONAGRACEAE. 

Ludwigia  alata  Ell. 
Ludwigia  microcarpa  Michx. 
Oenothera  huinifusa  Nutt. 

APIACEAE. 

Sanicula  sp. 

Hydrocotyle  umbellata,  L. 
Centella  asiaticc  (L.)  Urban. 

PRIMULACEAE. 

Samolus  florihundus  H.  B.  K. 

PLUMBAGINACEAE. 

Limonium  carolinianum  (Walt.)  Britton.     {Statice  limonium  var.  carolini- 
aniun  A.  Gray. ) 

LOGANIACEAE. 

Cynoctonum  mwreola  (L. )  Britton.     {Mitreola  petiolata  Torr.  &  Gr.) 
Polypremum  procumbens  L. 

ASCLEPIADACEAE. 

Vincetoxicum  palustre  (Pursh)  A.  Gray.     {Seiitera  maritima  Decne.) 

CONVOLVULACEAE. 
Ipomoea  sagittata  Cav. 


VERBENACEAE, 


Lippia  nodiflora  Michx. 
Callicarpa  americana  L. 


61  ri  THE    PLANT    COVEKING    OF    OCRACOKE    ISLAND. 

NEPETACEAE. 

Teucrimn  nashii  Kearney. 
Monarda  punctata  L. 

SOLANACEAE. 

Physalis  viscosa  L. 
Solanum  caroUnense  L. 

*  Solarium  nigrum  L. 

.    * Lycopersicum  esculentum  L. 

*  Datura  tatula  L. 

SCROPHULARIACEAE. 

*Verbascum  thapsusJj. 
Monniera  monniera  (L. )  Britton.     {Herpestis  monniera  H.  B.  K.) 
Gerardia  maritima  Raf . 

RUBIACEAE. 

Oldenlandia  uniflora  L.     (O.  glomerata  Michx.) 

Diodia  teres  Walt. 

Diodia  virginiana  L. 

Galium  sp.  (probably  G.  tinctorium  L.  or  G.  claytoni  Michx.). 

CUCURBITACEAE. 

*  Citrullus  vulgaris  Schrad. 
Melothria  pendula  L. 

CICHORIACEAE. 

Hier actum  gronovii  L. 

CARDUACEAE. 

Elephantopus  nudatus  A.  Gray. 
Mikania  scaudeiis  (L.)  Willd. 
SoUdago  sempervirens  L. 

Euthamia  caroliniana  (L.)  Greene.     {SoUdago  tenuifolia  Pursh.) 
Aster  salicifolius  Lam.  var. 
Aster  subidatus  Michx. 
Aster  tenuifoliris  L. 
Erigeron  canadensis  L. 
Baccharis  halimifolia  L. 
Pluchea  camphorata  (h.)  DC. 
Phichea  foetida  (L.)  B.  S.  P.     (P.  bifrons  DC.) 
Gnaphalium  purpureum  L. 
Ambrosia  artemisiaefolia  L. 
Iva  frutescens  L. 
Xanthium  sp. 
Xantliium  sp. 
Borrichia  frutescens  L. 
^Bidens  bipinnata  L. 
Ereclitites  liieracifolia  (L.)  Raf. 
Carduus  spinosissimus  Walt.     {Cnicus  horridulus  Pursh.) 


Library 
N.  estate  College 


WORKS    REFERRED    TO.  319 

BIBLIOGRAPHY. 

Britton,  N.  L.,  and  Brown,  A.  Illustrated  Flora  of  the  northern  United  States, 
Canada,  and  the  British  possessions.     181)0  to  189b. 

Contejean,  C.     Geo^raphie  Botaniqiie. .   1881. 

Diels,  L.  Stoffwechsel  und  Structur  der  Halophyten.  Jahrbiicher  fiir  wissen- 
schaf  tliche  Botanik.  23 :  J309  to  322.     1898. 

Duval-Jouve,  M.  J.  Etude  Anatomiiue  de  quel(iues  Graminees.  Memoires  de 
rAcademie  de  Montpellier,  7  :  309  to  400.  pis.  10  to  20.     18«;9. 

Duval-Jouve,  M.  J.  Histotaxie  des  Feuilles  des  Graminees.  Annaies  des  Sci- 
ences Naturelles,  Botanique,  ser.  0,  1 :  294  to  371,  pis.  10  to  19.     1875. 

Duval-Jouve,  M.  J.  Etude  histotaxique  des  Cyperus  de  France,  Memoires  de 
I'Academie  de  Montpellier,  8:  347  to  408,  pis.  19  to  22.     1874. 

Grisebach,  A.  Die  Vegetation  der  Erde  nach  ihrer  klimatischen  Anordnung. 
1872. 

Haberlandt,  G.     Physiologischa  Pflanzenanatomie.     1884. 

Holm,  Th.  A  Study  of  some  Anatomical  Characters  of  North  Americaii  Gram- 
ineae  —  II.  The  Genus  Uniola.    Coulter's  Botanical  Gazette,  16 :  219  to  225.    1,^91. 

Kerr,  W.  C.  The  Geology  of  Hatteras  and  the  Neighboring  Coast.  Bulletin 
Washington  Philosophical  Society,  6:  28  to  30.     1884. 

Lalanne,  G.  Recherches  sur  les  Caracteres  Anatomic^ues  des  Feuilles  Persis- 
tantes  des  Dicotyledones.     Bordeaux,  1890. 

Merriam^,  C.  H.  The  Geographic  Distribution  of  Animals  and  Plants  in  North 
America.  Yearbook  United  States  Department  of  Agriculture,  1894:  203  to  214. 
1895. 

Merrian^  C.  H.  Life  Zones  and  Crop  Zones.  Bulletin  United  States  Depart- 
ment of  Agriculture,  Division  Biological  Survey,  10:  1  to  73.     1898. 

Sachs,  J.  tJber  den  Einfluss  der  chemischen  und  physikalischen  Beschaffenheit 
des  Bodens  auf  die  Transpiration  der  Pflanzen.  Die  landwirthschaftlichen  Ver- 
suchsstationen,  1 :  203  to  240.     1859. 

Schimper,  A.  F.  W.  Botanische  Mitteilungen  aus  den  Tropen.  Heft  3.  Die 
indomalayische  Strand-Flora.     1891. 

Schimper,  A.  F.  W.     Pflanzengeographie  auf  phj^siologischer  Grundlage.     1898. 

Schwendener,  S.  Das  niechanische  Princip  im  anatomischen  Bau  der  Monocoty- 
len.     1874. 

Shaler,  N.  S.  The  Causes  which  have  led  to  the  Production  of  Cape  Hatteras. 
Proceedings  Boston  Society  Natural  History,  14:  110  to  121.     1872. 

Solereder,  H.     Systematische  Anatomic  der  Dicotyledonen.     1898-99. 

Volkens,  G.     Die  Flora  der  agyptisch-arabischen  Wiiste.     1887. 

Warming,  E.  Lehrbuch  der  iJkologischen  Pflanzengeographie.  (Deutsche  Aus- 
gabe.)     1890. 

Warming,  E.  Halofyt-Studier.  Memoires  de  TAcademie  Royale  de  Danemark, 
ser.  0,  8:  No.  4.     1897. 

Welch,  W.  L.  Opening  of  Hatteras  Inlet.  Bulletin  Essex  Institute.  17:  37  to 
42.     1880. 

Wiesner,  J.  Untersuchungen  iiber  den  Einfluss  des  Lichtes  und  der  strahlenden 
W;irme  anf  die  Transpiration  der  Pflanze.  Arbeiten  des  Pfiauzenphysiologischen 
Instituts  der  K.  K.  Wiener  Universit;;t.     1870. 


